Other Comprehensive Income (Loss) (Schedule of Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss) before reclassifications	$ (17)	$ (244)	$ (159)	$ (422)
Amounts reclassified from accumulated other comprehensive income	29	45	90	147
Other comprehensive (loss) income, net of tax	12	(199)	(69)	(275)
Unrealized Investment Gains
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	6	5	6	5
Other comprehensive income (loss) before reclassifications	1	1	1	1
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other comprehensive (loss) income, net of tax	1	1	1	1
Balance, ending of period	7	6	7	6
Pension/Postretirement Plans Gains (Losses)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(2,885)	(3,289)	(3,124)	(3,393)
Other comprehensive income (loss) before reclassifications	36	31	214	33
Amounts reclassified from accumulated other comprehensive income	29	45	90	147
Other comprehensive (loss) income, net of tax	65	76	304	180
Balance, ending of period	(2,820)	(3,213)	(2,820)	(3,213)
Foreign Currency Translation Adjustments
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(1,422)	(639)	(1,102)	(459)
Other comprehensive income (loss) before reclassifications	(54)	(276)	(374)	(456)
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other comprehensive (loss) income, net of tax	(54)	(276)	(374)	(456)
Balance, ending of period	(1,476)	(915)	(1,476)	(915)
AOCI Attributable to Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(4,301)	(3,923)	(4,220)	(3,847)
Other comprehensive (loss) income, net of tax			(69)	(275)
Balance, ending of period	$ (4,289)	$ (4,122)	$ (4,289)	$ (4,122)