Variable Interest Entities (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Variable Interest Entity [Line Items]
Carrying amounts of assets	$ 18,122	$ 22,295	$ 18,122	$ 22,295	$ 21,724
Carrying amounts of liabilities	15,085		15,085		18,530
Number of variable interest entities consolidated	0	0	0	0
Net realized gains (losses) related to deconsolidation	1	0	1	0
Variable Interest Entity Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Carrying amounts of assets	6,800		6,800		8,300
Carrying amounts of liabilities	5,700		5,700		7,300
Variable Interest Entity Non Primary Beneficiary [Member] | Financial Intermediary [Member]
Variable Interest Entity [Line Items]
VIE Assets	$ 135		$ 135