Debt (Principal Payments Due Under Investment Agreement Obligations) (Detail) (USD $) In Millions, unless otherwise specified			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Investment Agreement Obligations [Member]
Debt Instrument [Line Items]
2013			$ 182
2014			140
2015			45
2016			45
2017			53
Thereafter			561
Total expected principal payments	723	901	1,026	[1]
Less discount and other adjustments			82	[2]
Total			944
Discounts	1	1	115
Fair value adjustments			25
Accrued interest			$ 8

[1] Foreign currency denominated investment agreements are presented in U.S. dollars. Amounts reflect principal due at maturity for investment agreements issued at a discount.

[2] Includes discounts of $115 million on investment agreements, net fair value adjustments of $25 million and accrued interest of $8 million.