Investments in Securities Available-for-sale Securities 2 (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 38,767	[1]	$ 61,766	[1]
Gross unrealized gains	3,153		3,464
Gross unrealized losses - OTTI	(427)	[2]	(1,369)	[2]
Gross Unrealized Losses - Other	(493)	[3]	(680)	[3]
Available-for-sale, at fair value	41,000		63,181
Fannie Mae [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	6,800	[1]	9,580	[1]
Gross unrealized gains	446		871
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross Unrealized Losses - Other	(47)	[3]	(16)	[3]
Available-for-sale, at fair value	7,199
Freddie Mac [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	6,755	[1]	8,652	[1]
Gross unrealized gains	509		728
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross Unrealized Losses - Other	0	[3]	0	[3]
Available-for-sale, at fair value	7,264		9,380
Ginnie Mae [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	543	[1]	645	[1]
Gross unrealized gains	82		106
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross Unrealized Losses - Other	0	[3]	0	[3]
Available-for-sale, at fair value	625		751
Alt-A private-label securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	6,445	[1]	11,356	[1]
Gross unrealized gains	1,034		452
Gross unrealized losses - OTTI	(78)	[2]	(637)	[2]
Gross Unrealized Losses - Other	(2)	[3]	(96)	[3]
Available-for-sale, at fair value	7,399		11,075
Subprime private-label securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	6,418	[1]	8,137	[1]
Gross unrealized gains	765		217
Gross unrealized losses - OTTI	(144)	[2]	(669)	[2]
Gross Unrealized Losses - Other	(74)	[3]	(238)	[3]
Available-for-sale, at fair value	6,965		7,447
CMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	2,651	[1]	12,284	[1]
Gross unrealized gains	132		824
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross Unrealized Losses - Other	0	[3]	(11)	[3]
Available-for-sale, at fair value	2,783		13,097
Mortgage revenue bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	6,107	[1]	7,782	[1]
Gross unrealized gains	51		157
Gross unrealized losses - OTTI	(185)	[2]	(45)	[2]
Gross Unrealized Losses - Other	(171)	[3]	(52)	[3]
Available-for-sale, at fair value	5,802		7,842
Other mortgage-related securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	3,048	[1]	3,330	[1]
Gross unrealized gains	134		109
Gross unrealized losses - OTTI	(20)	[2]	(18)	[2]
Gross Unrealized Losses - Other	(199)	[3]	(267)	[3]
Available-for-sale, at fair value	2,963		3,154
Fannie Mae [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, at fair value	$ 7,199	[4]	$ 10,435	[4]

[1] Amortized cost consists of unpaid principal balance, unamortized premiums, discounts and other cost basis adjustments as well as net other-than-temporary impairments (“OTTI”) recognized in our condensed consolidated statements of operations and comprehensive income.

[2] Represents the noncredit component of other-than-temporary impairments losses recorded in “Accumulated other comprehensive income” as well as cumulative changes in fair value of securities for which we previously recognized the credit component of other-than-temporary impairments.

[3] Represents the gross unrealized losses on securities for which we have not recognized an other-than-temporary impairment.

[4] Contains securities recognized in our condensed consolidated balance sheets due to consolidation of certain multi-class resecuritization trusts.