Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Accumulated other comprehensive income (loss), end of period	$ (6,669)	$ (6,433)	$ (6,033)
Other comprehensive income (loss) before reclassifications	(367)
Amounts reclassified from accumulated other comprehensive (income) loss	131
Other comprehensive income (loss)	(236)
Foreign currency translation
Accumulated other comprehensive income (loss), end of period	90	456	401
Other comprehensive income (loss) before reclassifications	(366)
Amounts reclassified from accumulated other comprehensive (income) loss	0
Other comprehensive income (loss)	(366)
Pension and other postretirement benefits
Accumulated other comprehensive income (loss), end of period	(6,778)	(6,914)	(6,458)
Other comprehensive income (loss) before reclassifications	15
Amounts reclassified from accumulated other comprehensive (income) loss	121
Other comprehensive income (loss)	136
Derivative financial instruments
Accumulated other comprehensive income (loss), end of period	(62)	(42)	(38)
Other comprehensive income (loss) before reclassifications	(31)
Amounts reclassified from accumulated other comprehensive (income) loss	11
Other comprehensive income (loss)	(20)
Available-for-sale securities
Accumulated other comprehensive income (loss), end of period	81	67	62
Other comprehensive income (loss) before reclassifications	15
Amounts reclassified from accumulated other comprehensive (income) loss	(1)
Other comprehensive income (loss)	$ 14