Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), start of period	$ (6,431)	$ (3,898)
Other comprehensive income (loss) before reclassifications	(792)	32
Amounts reclassified from accumulated other comprehensive (income) loss	122	65
Other comprehensive income (loss)	(670)	97
Accumulated other comprehensive income (loss), end of period	(7,101)	(3,801)
Foreign currency translation
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), start of period	(988)	176
Other comprehensive income (loss) before reclassifications	(791)	40
Amounts reclassified from accumulated other comprehensive (income) loss	0	0
Other comprehensive income (loss)	(791)	40
Accumulated other comprehensive income (loss), end of period	(1,779)	216
Pension and other postretirement benefits
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), start of period	(5,407)	(4,152)
Other comprehensive income (loss) before reclassifications	5	0
Amounts reclassified from accumulated other comprehensive (income) loss	100	80
Other comprehensive income (loss)	105	80
Accumulated other comprehensive income (loss), end of period	(5,302)	(4,072)
Derivative financial instruments
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), start of period	(119)	(5)
Other comprehensive income (loss) before reclassifications	(14)	(16)
Amounts reclassified from accumulated other comprehensive (income) loss	24	(5)
Other comprehensive income (loss)	10	(21)
Accumulated other comprehensive income (loss), end of period	(109)	(26)
Available-for-sale securities
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), start of period	83	83
Other comprehensive income (loss) before reclassifications	8	8
Amounts reclassified from accumulated other comprehensive (income) loss	(2)	(10)
Other comprehensive income (loss)	6	(2)
Accumulated other comprehensive income (loss), end of period	$ 89	$ 81