Fair Value Option - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Fair Value, Options [Abstract]
Fixed rate debt accounted for under fair value option	$ 10,000,000,000		$ 10,000,000,000		$ 10,200,000,000
Long-term debt carried at fair value	9,500,000,000		9,500,000,000		9,700,000,000
Due to affiliate carried at fair value	478,000,000		478,000,000		514,000,000
Fair value option not elected related to fixed rate long-term debt	7,300,000,000		7,300,000,000		8,100,000,000
Aggregate unpaid principal balance of fixed rate debt accounted for under fair value option	9,300,000,000		9,300,000,000		9,400,000,000
Increased the debt balance			166,000,000		247,000,000
Foreign Currency Translation Gains (Losses) Recorded In Derivative Related Income Expense Associated With Debt Designated At Fair Value	(29,000,000)	144,000,000	81,000,000	84,000,000
Offsetting Gains (Losses) Recorded In Derivative Related Income Expense Associated With Related Derivatives	29,000,000	(144,000,000)	(81,000,000)	(84,000,000)
Cumulative increased value of debt through fair value option adjustments	$ 637,000,000		$ 637,000,000		$ 824,000,000