Employee Benefit Plans - Defined Benefit Plan, Information about Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Settlements	$ (6)	$ (15)
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			40.00%
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			60.00%
Corporate | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Settlements	0	0
RMBS | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Settlements	(5)	(14)
Foreign government | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Settlements	0	0
Mortgage loans | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Settlements	0	0
Other investments | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Settlements	(1)	(1)
Pension Benefits
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	4,641
Fair value of plan assets - end of year	3,563	4,641
Plan assets at fair value	4,641	4,641	$ 3,563	$ 4,641
Excluded investment payables			1	2
Excluded investment receivables			30	39
Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	993
Fair value of plan assets - end of year	973	993
Plan assets at fair value	993	993	973	993
Pension Benefits | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	3,054
Fair value of plan assets - end of year	2,049	3,054
Plan assets at fair value	3,054	3,054	2,049	3,054
Pension Benefits | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	167	107
Realized gains,net	2	1
Changes in unrealized gains, net	6	(3)
Purchases	36	109
Sales	(35)	(23)
Transfers into Level 3	2	5
Transfers out of Level 3	(11)	(14)
Fair value of plan assets - end of year	161	167
Plan assets at fair value	167	107	$ 161	167
Pension Benefits | Equity securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			35.00%
Pension Benefits | Equity securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			5.00%
Pension Benefits | Fixed income securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			70.00%
Pension Benefits | Fixed income securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			50.00%
Pension Benefits | Alternative assets | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			45.00%
Pension Benefits | Alternative assets | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			0.00%
Pension Benefits | Short-term investments
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			$ 189	311
Pension Benefits | Short-term investments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			21	12
Pension Benefits | Short-term investments | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			168	299
Pension Benefits | Short-term investments | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | Corporate
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			1,563	1,482
Pension Benefits | Corporate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | Corporate | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			1,549	1,469
Pension Benefits | Corporate | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	13	19
Realized gains,net	0	0
Changes in unrealized gains, net	2	0
Purchases	11	15
Sales	(12)	(10)
Transfers into Level 3	0	0
Transfers out of Level 3		(11)
Fair value of plan assets - end of year	14	13
Plan assets at fair value in the fair value hierarchy			14	13
Plan assets at fair value	13	19	14	13
Pension Benefits | RMBS
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			30	276
Pension Benefits | RMBS | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | RMBS | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			28	266
Pension Benefits | RMBS | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	10	24
Realized gains,net	0	0
Changes in unrealized gains, net	0	0
Purchases	1	0
Sales	(4)	0
Transfers into Level 3	0	2
Transfers out of Level 3	0	(2)
Fair value of plan assets - end of year	2	10
Plan assets at fair value in the fair value hierarchy			2	10
Plan assets at fair value	10	24	2	10
Pension Benefits | U.S. Treasuries
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			77	722
Pension Benefits | U.S. Treasuries | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			3	69
Pension Benefits | U.S. Treasuries | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			74	649
Pension Benefits | U.S. Treasuries | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	4
Pension Benefits | Foreign government
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			17	38
Pension Benefits | Foreign government | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | Foreign government | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			16	37
Pension Benefits | Foreign government | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	1	5
Realized gains,net	0	0
Changes in unrealized gains, net	0	0
Purchases	0	0
Sales	0	(4)
Transfers into Level 3	0	0
Transfers out of Level 3	0
Fair value of plan assets - end of year	1	1
Plan assets at fair value in the fair value hierarchy			1	1
Plan assets at fair value	1	5	1	1
Pension Benefits | CMBS
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			30	131
Pension Benefits | CMBS | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | CMBS | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			28	131
Pension Benefits | CMBS | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			2	0
Pension Benefits | Other fixed income
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			99	114
Pension Benefits | Other fixed income | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | Other fixed income | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			97	96
Pension Benefits | Other fixed income | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			2	18
Pension Benefits | Mortgage loans
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			140	121
Pension Benefits | Mortgage loans | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | Mortgage loans | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | Mortgage loans | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	121	54
Realized gains,net	0	0
Changes in unrealized gains, net	2	(3)
Purchases	17	70
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0
Fair value of plan assets - end of year	140	121
Plan assets at fair value in the fair value hierarchy			140	121
Plan assets at fair value	121	54	140	121
Pension Benefits | Other investments | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	22	5
Realized gains,net	2	1
Changes in unrealized gains, net	2	0
Purchases	7	24
Sales	(19)	(9)
Transfers into Level 3	2	3
Transfers out of Level 3	(11)	(1)
Fair value of plan assets - end of year	4	22
Plan assets at fair value	22	5	4	22
Pension Benefits | Large-cap domestic
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			684	696
Pension Benefits | Large-cap domestic | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			595	589
Pension Benefits | Large-cap domestic | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			89	107
Pension Benefits | Large-cap domestic | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | Mid-cap domestic
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			11	23
Pension Benefits | Mid-cap domestic | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			11	23
Pension Benefits | Mid-cap domestic | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | Mid-cap domestic | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | International
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			343	300
Pension Benefits | International | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			343	300
Pension Benefits | International | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | International | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			0	0
Pension Benefits | Total pension plan assets at fair value, in the fair value hierarchy
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			3,183	4,214
Pension Benefits | Total pension plan assets at fair value, in the fair value hierarchy | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			973	993
Pension Benefits | Total pension plan assets at fair value, in the fair value hierarchy | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			2,049	3,054
Pension Benefits | Total pension plan assets at fair value, in the fair value hierarchy | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at fair value in the fair value hierarchy			161	167
Pension Benefits | Private Market Alternatives
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at net asset value			168	87
Pension Benefits | Private Market Alternatives | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at net asset value			0	0
Pension Benefits | Private Market Alternatives | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at net asset value			0	0
Pension Benefits | Private Market Alternatives | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at net asset value			0	0
Pension Benefits | Hedge funds
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at net asset value			212	340
Pension Benefits | Hedge funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at net asset value			0	0
Pension Benefits | Hedge funds | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at net asset value			0	0
Pension Benefits | Hedge funds | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Plan assets at net asset value			0	0
Other Postretirement Benefits
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	137
Fair value of plan assets - end of year	113	137
Plan assets at fair value	137	137	113	137
Excluded investment payables			0
Excluded investment receivables			1	1
Other Postretirement Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	46
Fair value of plan assets - end of year	35	46
Plan assets at fair value	46	46	35	46
Other Postretirement Benefits | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	88
Fair value of plan assets - end of year	77	88
Plan assets at fair value	88	88	77	88
Other Postretirement Benefits | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	3	5
Changes in unrealized gains, net	0	0
Purchases	2	2
Settlements	(1)	(2)
Sales	(2)	(1)
Transfers into Level 3		0
Transfers out of Level 3	(1)	(1)
Fair value of plan assets - end of year	1	3
Plan assets at fair value	3	5	$ 1	3
Other Postretirement Benefits | Equity securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			45.00%
Other Postretirement Benefits | Equity securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			15.00%
Other Postretirement Benefits | Fixed income securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			85.00%
Other Postretirement Benefits | Fixed income securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			55.00%
Other Postretirement Benefits | Alternative assets | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			0.00%
Other Postretirement Benefits | Alternative assets | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation			0.00%
Other Postretirement Benefits | Short-term investments
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	4
Fair value of plan assets - end of year	4	4
Plan assets at fair value	4	4	$ 4	4
Other Postretirement Benefits | Short-term investments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	4
Fair value of plan assets - end of year	4	4
Plan assets at fair value	4	4	4	4
Other Postretirement Benefits | Short-term investments | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	0
Fair value of plan assets - end of year	0	0
Plan assets at fair value	0	0	0	0
Other Postretirement Benefits | Corporate
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	36
Fair value of plan assets - end of year	25	36
Plan assets at fair value	36	36	25	36
Other Postretirement Benefits | Corporate | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	35
Fair value of plan assets - end of year	25	35
Plan assets at fair value	35	35	25	35
Other Postretirement Benefits | Corporate | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	1	2
Changes in unrealized gains, net	0	0
Purchases	1	1
Settlements	0	0
Sales	(2)	(1)
Transfers into Level 3		0
Transfers out of Level 3	0	(1)
Fair value of plan assets - end of year	0	1
Plan assets at fair value	1	2	0	1
Other Postretirement Benefits | RMBS
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	25
Fair value of plan assets - end of year	17	25
Plan assets at fair value	25	25	17	25
Other Postretirement Benefits | RMBS | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	24
Fair value of plan assets - end of year	17	24
Plan assets at fair value	24	24	17	24
Other Postretirement Benefits | RMBS | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	1	3
Settlements	(1)	(2)
Sales	0
Transfers into Level 3		0
Transfers out of Level 3	0
Fair value of plan assets - end of year	0	1
Plan assets at fair value	1	3	0	1
Other Postretirement Benefits | U.S. Treasuries
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	19
Fair value of plan assets - end of year	26	19
Plan assets at fair value	19	19	26	19
Other Postretirement Benefits | U.S. Treasuries | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	5
Fair value of plan assets - end of year	1	5
Plan assets at fair value	5	5	1	5
Other Postretirement Benefits | U.S. Treasuries | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	14
Fair value of plan assets - end of year	25	14
Plan assets at fair value	14	14	25	14
Other Postretirement Benefits | Foreign government
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	2
Fair value of plan assets - end of year	1	2
Plan assets at fair value	2	2	1	2
Other Postretirement Benefits | Foreign government | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	2
Fair value of plan assets - end of year	1	2
Plan assets at fair value	2	2	1	2
Other Postretirement Benefits | Foreign government | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	0	0
Sales	0
Transfers into Level 3		0
Transfers out of Level 3	0
Fair value of plan assets - end of year	0	0
Plan assets at fair value	0	0	0	0
Other Postretirement Benefits | CMBS
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	9
Fair value of plan assets - end of year	5	9
Plan assets at fair value	9	9	5	9
Other Postretirement Benefits | CMBS | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	9
Fair value of plan assets - end of year	5	9
Plan assets at fair value	9	9	5	9
Other Postretirement Benefits | Other fixed income
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	5
Fair value of plan assets - end of year	5	5
Plan assets at fair value	5	5	5	5
Other Postretirement Benefits | Other fixed income | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	4
Fair value of plan assets - end of year	4	4
Plan assets at fair value	4	4	4	4
Other Postretirement Benefits | Other fixed income | Significant Unobservable Inputs (Level 3)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	1	0
Changes in unrealized gains, net	0	0
Purchases	1	1
Settlements	0
Sales	0	0
Transfers into Level 3		0
Transfers out of Level 3	(1)
Fair value of plan assets - end of year	1	1
Plan assets at fair value	1	0	1	1
Other Postretirement Benefits | Large-cap
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	37
Fair value of plan assets - end of year	30	37
Plan assets at fair value	37	37	30	37
Other Postretirement Benefits | Large-cap | Quoted Prices in Active Markets for Identical Assets (Level 1)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	37
Fair value of plan assets - end of year	30	37
Plan assets at fair value	37	37	30	37
Other Postretirement Benefits | Large-cap | Significant Observable Inputs (Level 2)
Pension Plan Asset Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
Fair value of plan assets - beginning of year	0
Fair value of plan assets - end of year	0	0
Plan assets at fair value	$ 0	$ 0	$ 0	$ 0