Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Tax benefit on unrecognized amounts	$ 1,800	$ 1,600	$ 531
Tax expense on recognition of previously deferred amounts	$ 469	$ 364	$ 304