Investments in Securities Trading 2 (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net trading gains (losses)	$ 396		$ 284
Net trading gains (losses) recorded in the period related to securities still held at period end	397		319
Mortgage-related securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net trading gains (losses)	391		296
Net trading gains (losses) recorded in the period related to securities still held at period end	392		331
Non-mortgage-related Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net trading gains (losses)	5	[1]	(12)	[1]
Net trading gains (losses) recorded in the period related to securities still held at period end	$ 5	[1]	$ (12)	[1]

[1] Consists of U.S. Treasury securities for the three months ended March 31, 2013 and U.S. Treasury securities and asset-backed securities for the three months ended March 31, 2012.