Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated other comprehensive income (loss) by component
Balance at the beginning of the period	$ (1,959)	$ (779)	$ (2,017)	$ (802)
OCI, before reclassifications, net of tax, attributable to parent	(10)	(16)	(10)	(7)
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	28	6	86	20
Other comprehensive income	18	(10)	76	13
Balance at the end of the period	(1,941)	(789)	(1,941)	(789)
Defined benefit plan | Pension plans
Accumulated other comprehensive income (loss) by component
Balance at the beginning of the period	(1,668)	(661)	(1,720)	(669)
OCI, before reclassifications, net of tax, attributable to parent	0	0	0	0
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	24	4	76	12
Other comprehensive income	24	4	76	12
Balance at the end of the period	(1,644)	(657)	(1,644)	(657)
Defined benefit plan | Post-retirement benefit plans
Accumulated other comprehensive income (loss) by component
Balance at the beginning of the period	(266)	(116)	(272)	(122)
OCI, before reclassifications, net of tax, attributable to parent	0	0	0	0
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	4	2	10	8
Other comprehensive income	4	2	10	8
Balance at the end of the period	(262)	(114)	(262)	(114)
Foreign currency translation adjustment and other
Accumulated other comprehensive income (loss) by component
Balance at the beginning of the period	(25)	(2)	(25)	(11)
OCI, before reclassifications, net of tax, attributable to parent	(10)	(16)	(10)	(7)
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	0	0	0	0
Other comprehensive income	(10)	(16)	(10)	(7)
Balance at the end of the period	$ (35)	$ (18)	$ (35)	$ (18)