Investments in Securities Available-for-sale Securities 1 (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 9		$ 18
Gross realized losses	4		9
Total proceeds	$ 94	[1]	$ 268	[1]

[1] Excludes proceeds from the initial sale of securities from new portfolio securitizations included in “Note 2, Consolidations and Transfers of Financial Assets.”