Retirement and Postemployment Benefits (Plan Assets and Expected Cash Flows) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member] | U.S. [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	$ 3,488	$ 3,243	$ 3,227	$ 3,488	$ 3,243
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	3,488	3,243	3,227
Balance at end of period		3,488	3,243
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract]
Employer contributions		$ 65	79
Amount to be contributed to plan in the next fiscal year				0
Expected amount of benefit payments in the next period for non-qualified plans				13
Estimated Future Benefit Payments (Details) [Abstract]
2018				260
2019				269
2020				268
2021				270
2022				272
2023-2027				1,328
Pension Plan [Member] | U.S. [Member] | Subsequent Event [Member]
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract]
Employer contributions	145
Pension Plan [Member] | U.S. [Member] | Master Trust [Member]
Assumptions Used in Calculations (Numeric) [Abstract]
The limited lives of four partnership of private equity investments (in years)		10 years
The amount of potential liability that maybe required to be funded by the master trust during life of the partnership				$ 28
Number Of Days Notice Required To Redeem Shares		45 days
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				100.00%	100.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				100.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	3,561	$ 3,381	3,381	$ 3,561	$ 3,381
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	3,561	3,381
Balance at end of period		3,561	3,381
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	716	714	714	716	714
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	716	714
Balance at end of period		716	714
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	931	909	909	931	909
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	931	909
Balance at end of period		931	909
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	37	40	42	37	40
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	37	40	42
Actual return on plan assets relating to assets still held at the reporting date		1	1
Purchases, sales and settlements		(4)	(3)
Balance at end of period		37	40
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				301	181
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				301	181
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				229	152
Measured at fair value using net asset value per share				364	272
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				229	152
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | International Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				538	551
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Commingled Debt Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				611	546
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				186	381
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				186	381
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				883	850
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				870	837
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				13	13
Fair value at end of period	13	13	10	13	13
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	13	13	10
Actual return on plan assets relating to assets still held at the reporting date		0	0
Purchases, sales and settlements		0	3
Balance at end of period		13	13
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				10	8
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				10	8
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Real Estate Alternative Investments [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				109	102
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Private Equity Alternative Investments [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				80	80
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Hedge Fund Of Funds Alternative Investments [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				175	167
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				50	61
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				50	61
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				1	3
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				1	3
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				24	27
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				24	27
Fair value at end of period	24	27	32	24	27
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	24	27	32
Actual return on plan assets relating to assets still held at the reporting date		1	1
Purchases, sales and settlements		(4)	(6)
Balance at end of period		24	27
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Receivables And Payables Net [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	72	(15)	(15)	72	(15)
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	72	(15)
Balance at end of period		72	(15)
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Account 401 H [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	(145)	(123)	(123)	(145)	(123)
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	(145)	(123)
Balance at end of period		(145)	(123)
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Total Trust Assets Not Including 401 H Assets [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	3,488	3,243	3,243	$ 3,488	$ 3,243
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	3,488	3,243
Balance at end of period		3,488	3,243
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				56.00%	52.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				55.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				32.00%	30.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Debt Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				14.00%	12.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Alternative Investments [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				10.00%	10.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				43.00%	46.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				43.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Debt Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				39.00%	43.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Derivatives [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				4.00%	3.00%
Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Liquidity Portfolio [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				1.00%	2.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				2.00%
Pension Plan [Member] | U.K. [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				100.00%	100.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				100.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	8,490	7,211	7,625	$ 8,490	$ 7,211
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	8,490	7,211	7,625
Balance at end of period		8,490	7,211
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract]
Employer contributions		$ 486	330
Amount to be contributed to plan in the next fiscal year				191
Recurrence of formal actuarial valuations (in years)		3 years
Percentage of deficit funding requirements permitted to recover in rates		78.00%
Estimated Future Benefit Payments (Details) [Abstract]
2018				343
2019				349
2020				353
2021				356
2022				362
2023-2027				1,843
Pension Plan [Member] | U.K. [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	216	$ 42	42	216	42
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	216	42
Balance at end of period		216	42
Pension Plan [Member] | U.K. [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	3,140	2,942	2,942	3,140	2,942
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	3,140	2,942
Balance at end of period		3,140	2,942
Pension Plan [Member] | U.K. [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	0	0	0	$ 0	$ 0
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	0	0
Balance at end of period		0	0
Pension Plan [Member] | U.K. [Member] | Cash And Cash Equivalents [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				2.00%	1.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				0.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				$ 216	$ 42
Pension Plan [Member] | U.K. [Member] | Cash And Cash Equivalents [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				216	42
Pension Plan [Member] | U.K. [Member] | Cash And Cash Equivalents [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.K. [Member] | Cash And Cash Equivalents [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				$ 0	$ 0
Pension Plan [Member] | U.K. [Member] | U.K. Companies Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				2.00%	3.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				2.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				$ 157	$ 210
Pension Plan [Member] | U.K. [Member] | European Companies Excluding U.K. Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				1.00%	2.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				1.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				$ 98	$ 177
Pension Plan [Member] | U.K. [Member] | Asian Pacific Companies Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				1.00%	2.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				1.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				$ 60	$ 140
Pension Plan [Member] | U.K. [Member] | North American Companies Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				1.00%	3.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				1.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				$ 123	$ 227
Pension Plan [Member] | U.K. [Member] | Emerging Markets Companies Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				1.00%	3.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				1.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				$ 62	$ 209
Pension Plan [Member] | U.K. [Member] | Global Equities Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				16.00%	6.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				10.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				$ 1,335	$ 466
Pension Plan [Member] | U.K. [Member] | Global Tactical Asset Allocation Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				33.00%	33.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				41.00%
Pension Plan [Member] | U.K. [Member] | Other Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				$ 2,807	$ 2,363
Pension Plan [Member] | U.K. [Member] | Debt Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				37.00%	41.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				38.00%
Pension Plan [Member] | U.K. [Member] | U.K. Corporate Bonds Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				$ 3	$ 2
Pension Plan [Member] | U.K. [Member] | U.K. Corporate Bonds Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.K. [Member] | U.K. Corporate Bonds Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				3	2
Pension Plan [Member] | U.K. [Member] | U.K. Corporate Bonds Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.K. [Member] | U.K. Gilts Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				3,137	2,940
Pension Plan [Member] | U.K. [Member] | U.K. Gilts Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Pension Plan [Member] | U.K. [Member] | U.K. Gilts Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				3,137	2,940
Pension Plan [Member] | U.K. [Member] | U.K. Gilts Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				$ 0	$ 0
Pension Plan [Member] | U.K. [Member] | Alternative Investments [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				6.00%	6.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				5.00%
Pension Plan [Member] | U.K. [Member] | Real Estate Alternative Investments [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				$ 492	$ 435
Other Postretirement Benefits Plan [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				100.00%	100.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				100.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	405	378	379	$ 405	$ 378
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	405	378	379
Balance at end of period		405	378
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract]
Employer contributions		$ 15	19
Amount to be contributed to plan in the next fiscal year				14
Estimated Future Benefit Payments (Details) [Abstract]
2018				51
2019				51
2020				50
2021				49
2022				48
2023-2027				218
Expected Federal Subsidy (Details) [Abstract]
Federal subsidy 2018				1
Federal subsidy 2019				0
Federal subsidy 2020				1
Federal subsidy 2021				0
Federal subsidy 2022				0
Federal subsidy 2023-2027				$ 2
Other Postretirement Benefits Plan [Member] | Cash And Cash Equivalents [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				4.00%	2.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				5.00%
Other Postretirement Benefits Plan [Member] | Money Market Funds [Member]
Assumptions Used in Calculations (Numeric) [Abstract]
Number of months from date of purchase that investment must mature		13 months
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	10	$ 5	5	$ 10	$ 5
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	10	5
Balance at end of period		10	5
Other Postretirement Benefits Plan [Member] | Money Market Funds [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				10	5
Other Postretirement Benefits Plan [Member] | Money Market Funds [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Other Postretirement Benefits Plan [Member] | Money Market Funds [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				$ 0	$ 0
Other Postretirement Benefits Plan [Member] | Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				47.00%	48.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				45.00%
Other Postretirement Benefits Plan [Member] | United States Large Cap Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				$ 123	$ 123
Other Postretirement Benefits Plan [Member] | Commingled Debt Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				$ 96	$ 114
Other Postretirement Benefits Plan [Member] | Debt Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				49.00%	50.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				50.00%
Other Postretirement Benefits Plan [Member] | Corporate Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	30	0	0	$ 30	$ 0
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	30	0
Balance at end of period		30	0
Other Postretirement Benefits Plan [Member] | Corporate Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Other Postretirement Benefits Plan [Member] | Corporate Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				30	0
Other Postretirement Benefits Plan [Member] | Corporate Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Other Postretirement Benefits Plan [Member] | Municipalities Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	12
Other Postretirement Benefits Plan [Member] | Municipalities Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Other Postretirement Benefits Plan [Member] | Municipalities Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	12
Other Postretirement Benefits Plan [Member] | Municipalities Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Other Postretirement Benefits Plan [Member] | Receivables And Payables Net [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	1	1	1	1	1
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	1	1
Balance at end of period		1	1
Other Postretirement Benefits Plan [Member] | Account 401 H [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	145	123	123	145	123
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	145	123
Balance at end of period		145	123
Other Postretirement Benefits Plan [Member] | Total Trust Assets Not Including 401 H Assets [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	259	254	254	259	254
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	259	254
Balance at end of period		259	254
Other Postretirement Benefits Plan [Member] | Total Trust Assets Not Including 401 H Assets [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	10	5	5	10	5
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	10	5
Balance at end of period		10	5
Other Postretirement Benefits Plan [Member] | Total Trust Assets Not Including 401 H Assets [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	30	12	12	30	12
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	30	12
Balance at end of period		30	12
Other Postretirement Benefits Plan [Member] | Total Trust Assets Not Including 401 H Assets [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	0	0	0	0	0
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	0	0
Balance at end of period		$ 0	$ 0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | Master Trust [Member]
Information About Plan Assets (Numeric) [Abstract]
Undivided interest percentage in each asset category that PPL subsidiary holds		40.00%	41.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	1,402	$ 1,315	$ 1,289	1,402	1,315
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	1,402	1,315	1,289
Balance at end of period		1,402	1,315
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract]
Employer contributions		$ 21	66
Amount to be contributed to plan in the next fiscal year				0
Expected amount of benefit payments in the next period for non-qualified plans				4
Estimated Future Benefit Payments (Details) [Abstract]
2018				109
2019				113
2020				114
2021				115
2022				116
2023-2027				573
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Subsequent Event [Member]
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract]
Employer contributions	105
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member]
Information About Plan Assets (Numeric) [Abstract]
Value of plan U.S. pension trust assets that relate to PPL subsidiary				1,400	$ 1,300
Assumptions Used in Calculations (Numeric) [Abstract]
The limited lives of four partnership of private equity investments (in years)		10 years
The amount of potential liability that maybe required to be funded by the master trust during life of the partnership				$ 28
Number Of Days Notice Required To Redeem Shares		45 days
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				100.00%	100.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				100.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	3,561	$ 3,381	3,381	$ 3,561	$ 3,381
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	3,561	3,381
Balance at end of period		3,561	3,381
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	716	714	714	716	714
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	716	714
Balance at end of period		716	714
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	931	909	909	931	909
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	931	909
Balance at end of period		931	909
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	37	40	42	37	40
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	37	40	42
Actual return on plan assets relating to assets still held at the reporting date		1	1
Purchases, sales and settlements		(4)	(3)
Balance at end of period		37	40
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				301	181
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				301	181
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				229	152
Measured at fair value using net asset value per share				364	272
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				229	152
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | International Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				538	551
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Commingled Debt Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				611	546
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				186	381
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				186	381
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				883	850
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				870	837
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				13	13
Fair value at end of period			10
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period			10
Actual return on plan assets relating to assets still held at the reporting date		0	0
Purchases, sales and settlements		0	3
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				10	8
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				10	8
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Real Estate Alternative Investments [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				109	102
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Private Equity Alternative Investments [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				80	80
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Hedge Fund Of Funds Alternative Investments [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				175	167
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				50	61
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				50	61
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				1	3
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				1	3
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				24	27
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				24	27
Fair value at end of period			32
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period			32
Actual return on plan assets relating to assets still held at the reporting date		1	1
Purchases, sales and settlements		(4)	(6)
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Receivables And Payables Net [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	72	(15)	(15)	72	(15)
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	72	(15)
Balance at end of period		72	(15)
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Account 401 H [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	(145)	(123)	(123)	(145)	(123)
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	(145)	(123)
Balance at end of period		(145)	(123)
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Total Trust Assets Not Including 401 H Assets [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	3,488	3,243	3,243	$ 3,488	$ 3,243
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	3,488	3,243
Balance at end of period		3,488	3,243
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				56.00%	52.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				55.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				32.00%	30.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Debt Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				14.00%	12.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Alternative Investments [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				10.00%	10.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				43.00%	46.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				43.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Debt Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				39.00%	43.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Derivatives [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				4.00%	3.00%
LG And E And KU Energy LLC [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Liquidity Portfolio [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				1.00%	2.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				2.00%
LG And E And KU Energy LLC [Member] | Other Postretirement Benefits Plan [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	116	98	88	$ 116	$ 98
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	116	98	88
Balance at end of period		116	98
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract]
Employer contributions		15	20
Amount to be contributed to plan in the next fiscal year				14
Estimated Future Benefit Payments (Details) [Abstract]
2018				14
2019				15
2020				16
2021				16
2022				16
2023-2027				79
Expected Federal Subsidy (Details) [Abstract]
Federal subsidy 2018				0
Federal subsidy 2019				0
Federal subsidy 2020				1
Federal subsidy 2021				0
Federal subsidy 2022				0
Federal subsidy 2023-2027				2
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	325	318	297	325	318
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	325	318	297
Balance at end of period		325	318
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract]
Employer contributions		$ 0	$ 35
Amount to be contributed to plan in the next fiscal year				0
Estimated Future Benefit Payments (Details) [Abstract]
2018				26
2019				26
2020				26
2021				25
2022				24
2023-2027				104
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Subsequent Event [Member]
Defined Benefit Plan Estimated Future Employer Contributions (Numeric) [Abstract]
Employer contributions	54
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member]
Information About Plan Assets (Numeric) [Abstract]
Value of plan U.S. pension trust assets that relate to PPL subsidiary				325	$ 318
Undivided interest percentage in each asset category that PPL subsidiary holds		9.00%	10.00%
Assumptions Used in Calculations (Numeric) [Abstract]
The limited lives of four partnership of private equity investments (in years)		10 years
The amount of potential liability that maybe required to be funded by the master trust during life of the partnership				$ 28
Number Of Days Notice Required To Redeem Shares		45 days
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				100.00%	100.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				100.00%
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	3,561	$ 3,381	$ 3,381	$ 3,561	$ 3,381
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	3,561	3,381
Balance at end of period		3,561	3,381
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	716	714	714	716	714
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	716	714
Balance at end of period		716	714
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	931	909	909	931	909
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	931	909
Balance at end of period		931	909
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	37	40	42	37	40
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	37	40	42
Actual return on plan assets relating to assets still held at the reporting date		1	1
Purchases, sales and settlements		(4)	(3)
Balance at end of period		37	40
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				301	181
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				301	181
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Cash And Cash Equivalents [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				229	152
Measured at fair value using net asset value per share				364	272
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				229	152
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Equity Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | International Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				538	551
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Commingled Debt Equity Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				611	546
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				186	381
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				186	381
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | US Treasury And US Government Sponsored Agency Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				883	850
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				870	837
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Corporate Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				13	13
Fair value at end of period			10
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period			10
Actual return on plan assets relating to assets still held at the reporting date		0	0
Purchases, sales and settlements		0	3
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				10	8
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				10	8
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Debt Securities [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Real Estate Alternative Investments [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				109	102
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Private Equity Alternative Investments [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				80	80
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Hedge Fund Of Funds Alternative Investments [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value using net asset value per share				175	167
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				50	61
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				50	61
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Interest Rate Swaps And Swaptions Derivatives [ Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				1	3
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				1	3
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Other Derivatives [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				24	27
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 1 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 2 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				0	0
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Insurance Contracts [Member] | Level 3 [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Measured at fair value not using net asset value per share				24	27
Fair value at end of period			32
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period			32
Actual return on plan assets relating to assets still held at the reporting date		1	1
Purchases, sales and settlements		(4)	(6)
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Receivables And Payables Net [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	72	(15)	(15)	72	(15)
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	72	(15)
Balance at end of period		72	(15)
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Account 401 H [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	(145)	(123)	(123)	(145)	(123)
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	(145)	(123)
Balance at end of period		(145)	(123)
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Total Trust Assets Not Including 401 H Assets [Member]
Defined benefit plan fair value of plan assets (Details) [Abstract]
Fair value at end of period	3,488	3,243	3,243	$ 3,488	$ 3,243
Change in Fair Value of Level 3 Plan Assets [Roll Forward]
Balance at beginning of period	$ 3,488	3,243
Balance at end of period		$ 3,488	$ 3,243
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				56.00%	52.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				55.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Equity Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				32.00%	30.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Debt Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				14.00%	12.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Growth Portfolio [Member] | Alternative Investments [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				10.00%	10.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				43.00%	46.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				43.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Debt Securities [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				39.00%	43.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Immunizing Portfolio [Member] | Derivatives [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				4.00%	3.00%
Louisville Gas And Electric Co [Member] | Pension Plan [Member] | U.S. [Member] | Master Trust [Member] | Liquidity Portfolio [Member]
Actual Allocation by Plan Asset (Details) [Abstract]
Percentage of trust assets				1.00%	2.00%
Target Allocations (Details ) [Abstract]
Target asset allocation				2.00%