Other Comprehensive Income (Loss) (Schedule of Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss) before reclassifications	$ 226	$ 93
Amounts reclassified from accumulated other comprehensive income	30	30
Other comprehensive income, net of tax	256	123
Unrealized Investment Gains
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	19	6
Other comprehensive income (loss) before reclassifications	(3)	0
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income, net of tax	(3)	0
Balance, ending of period	16	6
Pension/Postretirement Plans Gains (Losses)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(3,232)	(3,124)
Other comprehensive income (loss) before reclassifications	(6)	80
Amounts reclassified from accumulated other comprehensive income	30	30
Other comprehensive income, net of tax	24	110
Balance, ending of period	(3,208)	(3,014)
Foreign Currency Translation Adjustments
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(1,880)	(1,102)
Other comprehensive income (loss) before reclassifications	235	13
Amounts reclassified from accumulated other comprehensive income	0	0
Other comprehensive income, net of tax	235	13
Balance, ending of period	(1,645)	(1,089)
AOCI Attributable to Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(5,093)	(4,220)
Other comprehensive income, net of tax	256	123
Balance, ending of period	$ (4,837)	$ (4,097)