Preferred stock- Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Class of Stock [Line Items]
Preferred stock, shares authorized (shares)	100,000,000		100,000,000
Preferred stock, par value (usd per share)	$ 0.01		$ 0.01
Carrying value	$ 1,562	[1]	$ 1,562	[1]
Series A Preferred Stock
Class of Stock [Line Items]
Carrying value	500	[1]	500	[1]
Series C Noncumulative Perpetual Preferred Stock
Class of Stock [Line Items]
Carrying value	$ 568	[1]	$ 568	[1]
Preferred Stock Redemption Period Following Regulatory Capital Treatment Event	90 days

[1] The carrying value of the Series C and Series D preferred stock is recorded net of issuance costs.