Reclassifications out of Accumulated Other Comprehensive Loss Changes in Accumulated Other Comprehensive Loss by Component (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Changes in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	$ (4,143)	$ (3,947)
Other comprehensive income (loss) before reclassifications	(107)	(92)
Amounts reclassified from accumulated other comprehensive loss	40	121
Purchase of subsidiary shares from minority interest		(1)
Balance at end of period	(4,210)	(3,919)
Foreign Currency Translation Adjustment
Changes in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(894)	(690)
Other comprehensive income (loss) before reclassifications	(140)	(117)
Amounts reclassified from accumulated other comprehensive loss	2	2
Purchase of subsidiary shares from minority interest		(1)
Balance at end of period	(1,032)	(806)
Unrecognized Net Actuarial Losses and Prior Service Costs
Changes in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(3,297)	(3,290)
Other comprehensive income (loss) before reclassifications	22	17
Amounts reclassified from accumulated other comprehensive loss	55	118
Purchase of subsidiary shares from minority interest		0
Balance at end of period	(3,220)	(3,155)
Deferred Derivative Gains (Losses)
Changes in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	12	(1)
Other comprehensive income (loss) before reclassifications	14	8
Amounts reclassified from accumulated other comprehensive loss	(17)	1
Purchase of subsidiary shares from minority interest		0
Balance at end of period	9	8
Unrealized Investment Gains
Changes in Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	36	34
Other comprehensive income (loss) before reclassifications	(3)	0
Amounts reclassified from accumulated other comprehensive loss	0	0
Purchase of subsidiary shares from minority interest		0
Balance at end of period	$ 33	$ 34