Employee Benefit Plans - Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Domestic Pension Plans [Member]
Defined Benefit Plan, Funded Status of Plan [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	$ 2,718	$ 2,711	$ 2,711	$ 2,489	$ 2,718
Defined Benefit Plan, Benefit Obligation	3,119	2,821	2,821	2,934	3,119
Defined Benefit Plan, Funded Status of Plan				(445)	(401)
Other assets				7	12
Other current liabilities				(15)	(14)
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent				(437)	(399)
Defined Benefit Plan, Amounts Recognized in Balance Sheet				(445)	(401)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	2,718	2,711
Defined Benefit Plan, Contributions by Employer	13	37
Defined Benefit Plan, Contributions by Plan Participants	0	0
Defined Benefit Plan, Actual Return on Plan Assets	(17)	188
Defined Benefit Plan, Settlements, Plan Assets	(23)	0
Defined Benefit Plan, Benefits Paid	(202)	(218)
Ending balance	2,489	2,718	2,711
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	3,119	2,821
Defined Benefit Plan, Service Cost	33	36	24
Defined Benefit Plan, Interest Cost	121	131	87
Defined Benefit Plan, Contributions by Plan Participants	0	0
Defined Benefit Plan, Actuarial Gain (Loss)	(110)	349
Defined Benefit Plan, Plan Amendments	(4)	0
Defined Benefit Plan, Settlements, Benefit Obligation	(23)	0
Benefits Paid	(202)	(218)
Ending balance	2,934	3,119	2,821
Defined Benefit Plan, Accumulated Benefit Obligation				2,906	3,086
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets [Abstract]
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets, Aggregate Fair Value of Plan Assets				1,811	1,987
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets, Aggregate Benefit Obligation				2,263	2,401
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Accumulated Benefit Obligation				2,244	2,380
Domestic Other Postretirement Plans [Member]
Defined Benefit Plan, Funded Status of Plan [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	858	852	852	662	858
Defined Benefit Plan, Benefit Obligation	936	987	987	740	936
Defined Benefit Plan, Funded Status of Plan				(78)	(78)
Other assets				15	10
Other current liabilities				0	0
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent				(93)	(88)
Defined Benefit Plan, Amounts Recognized in Balance Sheet				(78)	(78)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	858	852
Defined Benefit Plan, Contributions by Employer	2	2
Defined Benefit Plan, Contributions by Plan Participants	9	11
Defined Benefit Plan, Actual Return on Plan Assets	0	54
Defined Benefit Plan, Settlements, Plan Assets	(150)	0
Defined Benefit Plan, Benefits Paid	(57)	(61)
Ending balance	662	858	852
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	936	987
Defined Benefit Plan, Service Cost	11	14	14
Defined Benefit Plan, Interest Cost	31	46	33
Defined Benefit Plan, Contributions by Plan Participants	9	11
Defined Benefit Plan, Actuarial Gain (Loss)	(43)	(61)
Defined Benefit Plan, Plan Amendments	3	0
Defined Benefit Plan, Settlements, Benefit Obligation	(150)	0
Benefits Paid	(57)	(61)
Ending balance	740	936	987
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets [Abstract]
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets, Aggregate Fair Value of Plan Assets				413	598
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets, Aggregate Benefit Obligation				505	686
Domestic Other Postretirement Plans [Member] | PacifiCorp [Member]
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets [Abstract]
Defined Benefit Plan, Amount To Be Transferred				150
UK Pension Plans [Member]
Defined Benefit Plan, Funded Status of Plan [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	2,368	2,177	2,177	2,276	2,368
Defined Benefit Plan, Benefit Obligation	2,279	2,185	2,185	2,142	2,279
Defined Benefit Plan, Funded Status of Plan				134	89
Other assets				134	89
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	2,368	2,177
Defined Benefit Plan, Contributions by Employer	77	89
Defined Benefit Plan, Contributions by Plan Participants	2	2
Defined Benefit Plan, Actual Return on Plan Assets	48	337
Defined Benefit Plan, Benefits Paid	(91)	(92)
Foreign Currency Exchange Rate Changes	(128)	(145)
Ending balance	2,276	2,368	2,177
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning balance	2,279	2,185
Defined Benefit Plan, Service Cost	24	24	22
Defined Benefit Plan, Interest Cost	79	95	85
Defined Benefit Plan, Contributions by Plan Participants	2	2
Defined Benefit Plan, Actuarial Gain (Loss)	(30)	205
Benefits Paid	(91)	(92)
Foreign currency exchange rate changes	(121)	(140)
Ending balance	$ 2,142	$ 2,279	$ 2,185
Defined Benefit Plan, Accumulated Benefit Obligation				1,891	2,019
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plans, Supplemental Employee Retirement Plans [Abstract]
Life Insurance, Corporate or Bank Owned, Amount				$ 228	$ 247