Comprehensive Income (Loss) (Reclassification Out of AOCI) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes		$ (38)	$ 52	$ (185)	$ 165
Tax impact		24	(10)	92	(46)
Net income (loss)				(93)	119
Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension Benefits [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Actuarial gains (losses)	[1],[2]	(9)	(5)	(22)	(14)
Tax impact	[1],[2]	3	2	8	5
Net income (loss)	[1],[2]	(6)	(3)	(14)	(9)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Postretirement Costs [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior-service costs	[1],[2]	1	1	3	3
Actuarial gains (losses)	[1],[2]	$ (1)	$ (1)	(6)	(2)
Income before income taxes	[1],[2]			(3)	1
Tax impact	[1],[2]			1
Net income (loss)	[1],[2]			$ (2)	$ 1

[1] Amounts in parentheses indicate losses.

[2] These accumulated other comprehensive loss components are included in the computation of net periodic pension and OPEB costs (see Note 14 - Retirement Plans for additional details).