Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), start of period	$ (6,729)	$ (3,683)	$ (6,431)	$ (3,898)
Other comprehensive income (loss) before reclassifications	(216)	(741)	(760)	(666)
Amounts reclassified from accumulated other comprehensive (income) loss	102	67	348	207
Other comprehensive income (loss)	(114)	(674)	(412)	(459)
Accumulated other comprehensive income (loss), end of period	(6,843)	(4,357)	(6,843)	(4,357)
Foreign currency translation
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), start of period	(1,555)	244	(988)	176
Other comprehensive income (loss) before reclassifications	(234)	(710)	(801)	(642)
Amounts reclassified from accumulated other comprehensive (income) loss	0	0	0	0
Other comprehensive income (loss)	(234)	(710)	(801)	(642)
Accumulated other comprehensive income (loss), end of period	(1,789)	(466)	(1,789)	(466)
Pension and other postretirement benefits
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), start of period	(5,183)	(3,981)	(5,407)	(4,152)
Other comprehensive income (loss) before reclassifications	45	4	69	15
Amounts reclassified from accumulated other comprehensive (income) loss	100	80	300	240
Other comprehensive income (loss)	145	84	369	255
Accumulated other comprehensive income (loss), end of period	(5,038)	(3,897)	(5,038)	(3,897)
Derivative financial instruments
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), start of period	(73)	(42)	(119)	(5)
Other comprehensive income (loss) before reclassifications	(12)	(30)	(15)	(57)
Amounts reclassified from accumulated other comprehensive (income) loss	20	0	69	(10)
Other comprehensive income (loss)	8	(30)	54	(67)
Accumulated other comprehensive income (loss), end of period	(65)	(72)	(65)	(72)
Available-for-sale securities
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), start of period	82	96	83	83
Other comprehensive income (loss) before reclassifications	(15)	(5)	(13)	18
Amounts reclassified from accumulated other comprehensive (income) loss	(18)	(13)	(21)	(23)
Other comprehensive income (loss)	(33)	(18)	(34)	(5)
Accumulated other comprehensive income (loss), end of period	$ 49	$ 78	$ 49	$ 78