Other Comprehensive Income (Loss) (Schedule of Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ (4,220)	$ (3,847)
Other comprehensive income (loss) before reclassifications	93	(295)
Amounts reclassified from accumulated other comprehensive income	30	52
Other comprehensive income (loss), net of tax	123	(243)
Balance, end of period	(4,097)	(4,090)
Unrealized Investment Gains
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	6	5
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income (loss), net of tax	0	0
Balance, end of period	6	5
Pension/Postretirement Plans Gains (Losses)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(3,124)	(3,393)
Other comprehensive income (loss) before reclassifications	80	128
Amounts reclassified from accumulated other comprehensive income	30	52
Other comprehensive income (loss), net of tax	110	180
Balance, end of period	(3,014)	(3,213)
Foreign Currency Translation Adjustments
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(1,102)	(459)
Other comprehensive income (loss) before reclassifications	13	(423)
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income (loss), net of tax	13	(423)
Balance, end of period	$ (1,089)	$ (882)