Securities - Securities Held to Maturity with Continuous Unrealized Loss Position (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	$ 874
Less than 12 months, Unrealized Losses, Not Recognized in OCI	17
12 months or more, Fair Value	17
12 months or more, Unrealized Losses, Recognized in OCI	2
Total, Fair Value	891
Total, Unrealized Losses, Recognized in OCI	2	17
Total, Unrealized Losses, Not Recognized in OCI	17
Collateralized loan obligations (CLOs) [Member]
Schedule of Held-to-maturity Securities [Line Items]
12 months or more, Fair Value	17	121
12 months or more, Unrealized Losses, Recognized in OCI	2	17
Total, Fair Value	17	121
Total, Unrealized Losses, Recognized in OCI	2	17
U.S. government agency and government sponsored agencies-residential mortgage backed securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, Fair Value	874
Less than 12 months, Unrealized Losses, Not Recognized in OCI	17
Total, Fair Value	874
Total, Unrealized Losses, Not Recognized in OCI	$ 17