Pension and Other Postretirement Benefits (Components of Net Periodic Benefit Cost and Amounts Recognized in Other Comprehensive Income (Loss) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Settlements	$ 211,000,000	$ 0	$ 0
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax [Abstract]
Deferred income taxes	(3,000,000)	19,000,000	105,000,000
Pension benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	29,000,000	31,000,000	31,000,000
Interest cost	215,000,000	209,000,000	237,000,000
Expected return on plan assets	(227,000,000)	(261,000,000)	(262,000,000)
Amortization of actuarial losses (gains)	84,000,000	79,000,000	63,000,000
Amortization of prior service cost (credit)	1,000,000	1,000,000	1,000,000
Settlements	211,000,000	0	0
Net periodic cost	313,000,000	59,000,000	70,000,000
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year [Abstract]
Estimated net actuarial (gain) loss that will be amortized into net periodic benefit cost over next fiscal year	101,000,000
Estimated net prior service cost (credit) that will be amortized into net periodic benefit cost over the next fiscal year	1,000,000
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax [Abstract]
Actuarial (losses) gains	(275,000,000)
Amortization of actuarial losses (gains)	84,000,000
Amortization of prior service (credit) cost	1,000,000
Settlements	211,000,000
Cumulative translation adjustments	2,000,000
Recognized in other comprehensive income, before tax	23,000,000
Deferred income taxes	(9,000,000)
Recognized in other comprehensive income, net of tax	14,000,000
Postretirement benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0
Interest cost	20,000,000	20,000,000	25,000,000
Expected return on plan assets	0	0	0
Amortization of actuarial losses (gains)	(21,000,000)	(21,000,000)	(21,000,000)
Amortization of prior service cost (credit)	0	0	(1,000,000)
Settlements	0	0	0
Net periodic cost	(1,000,000)	$ (1,000,000)	$ 3,000,000
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year [Abstract]
Estimated net actuarial (gain) loss that will be amortized into net periodic benefit cost over next fiscal year	(22,000,000)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax [Abstract]
Actuarial (losses) gains	5,000,000
Amortization of actuarial losses (gains)	(21,000,000)
Amortization of prior service (credit) cost	0
Settlements	0
Cumulative translation adjustments	0
Recognized in other comprehensive income, before tax	(16,000,000)
Deferred income taxes	6,000,000
Recognized in other comprehensive income, net of tax	$ (10,000,000)