Other Comprehensive Income (Loss) (Schedule of Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ (3,923)	$ (2,607)	$ (3,847)	$ (2,621)
Other comprehensive income (loss) before reclassifications	(244)	(325)	(422)	(378)
Amounts reclassified from accumulated other comprehensive income	45	37	147	104
Other comprehensive (loss) income, net of tax	(199)	(288)	(275)	(274)
Balance, end of period	(4,122)	(2,895)	(4,122)	(2,895)
Unrealized Investment Gains [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	5	5	5	5
Other comprehensive income (loss) before reclassifications	1	0	1	0
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other comprehensive (loss) income, net of tax	1	0	1	0
Balance, end of period	6	5	6	5
Pension/Postretirement Plans Gains (Losses) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(3,289)	(2,883)	(3,393)	(2,682)
Other comprehensive income (loss) before reclassifications	31	94	33	(174)
Amounts reclassified from accumulated other comprehensive income	45	37	147	104
Other comprehensive (loss) income, net of tax	76	131	180	(70)
Balance, end of period	(3,213)	(2,752)	(3,213)	(2,752)
Foreign Currency Translation Adjustments [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(639)	271	(459)	56
Other comprehensive income (loss) before reclassifications	(276)	(419)	(456)	(204)
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other comprehensive (loss) income, net of tax	(276)	(419)	(456)	(204)
Balance, end of period	$ (915)	$ (148)	$ (915)	$ (148)