Accumulated Other Comprehensive Income - Components of Accumulated Other Comprehensive Income Included in Shareholders' Equity (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Income Loss [Line Items]
Taxes on accumulated unrealized loss on derivative instruments	$ (48)	$ (39)	$ (20)
Taxes on accumulated unrealized gain on available-for-sale securities	3	1	3
Taxes on funded status of post-retirement benefit obligations	$ (11)	$ (9)	$ (4)