Investments in Securities Available-for-sale Securities 2 (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 30,903	[1]	$ 35,690	[1]
Gross unrealized gains	3,570		3,364
Gross unrealized losses - OTTI	(187)	[2]	(385)	[2]
Gross unrealized losses - Other	(260)	[3]	(498)	[3]
Available-for-sale, at fair value	34,026		38,171
Fannie Mae [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	5,663	[1]	6,227	[1]
Gross unrealized gains	385		390
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross unrealized losses - Other	(26)	[3]	(44)	[3]
Available-for-sale, at fair value	6,022		6,573
Freddie Mac [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	5,735	[1]	6,365	[1]
Gross unrealized gains	467		477
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross unrealized losses - Other	0	[3]	0	[3]
Available-for-sale, at fair value	6,202		6,842
Ginnie Mae [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	461	[1]	512	[1]
Gross unrealized gains	67		76
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross unrealized losses - Other	0	[3]	0	[3]
Available-for-sale, at fair value	528		588
Alt-A private-label securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	5,479	[1]	6,240	[1]
Gross unrealized gains	1,220		1,151
Gross unrealized losses - OTTI	(18)	[2]	(40)	[2]
Gross unrealized losses - Other	0	[3]	(2)	[3]
Available-for-sale, at fair value	6,681		7,349
Subprime private-label securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	4,688	[1]	6,232	[1]
Gross unrealized gains	1,057		991
Gross unrealized losses - OTTI	(19)	[2]	(102)	[2]
Gross unrealized losses - Other	(21)	[3]	(53)	[3]
Available-for-sale, at fair value	5,705		7,068
CMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	1,427	[1]	1,526	[1]
Gross unrealized gains	81		80
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross unrealized losses - Other	0	[3]	0	[3]
Available-for-sale, at fair value	1,508		1,606
Mortgage revenue bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	4,669	[1]	5,645	[1]
Gross unrealized gains	79		35
Gross unrealized losses - OTTI	(126)	[2]	(228)	[2]
Gross unrealized losses - Other	(62)	[3]	(196)	[3]
Available-for-sale, at fair value	4,560		5,256
Other mortgage-related securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	2,781	[1]	2,943	[1]
Gross unrealized gains	214		164
Gross unrealized losses - OTTI	(24)	[2]	(15)	[2]
Gross unrealized losses - Other	(151)	[3]	(203)	[3]
Available-for-sale, at fair value	$ 2,820		$ 2,889

[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” in our condensed consolidated balance sheets, 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 other-than-temporary impairments.