Subsequent Event - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended				12 Months Ended		1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 21, 2013 Subsequent Event [Member]	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2012 Maximum [Member]	Feb. 21, 2013 Victory Capital [Member] Subsequent Event [Member]
Subsequent Event [Line Items]
Sale of investment management subsidiary and broker-dealer affiliate	$ 1	$ 1,667	$ 142				$ 246
Purchase price of cash				201
Purchase price of seller note payable				45
Estimated after-tax gain					145	155
Business sold revenues	112
Business acquired expenses	$ 88