Investments in Securities Available-for-sale Securities 2 (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 69,905	[1]	$ 78,845	[1]
Gross unrealized gains	3,093		3,150
Gross unrealized losses - OTTI	(2,277)	[2]	(3,250)	[2]
Gross unrealized losses, other	(1,027)	[3]	(1,163)	[3]
Available-for-sale, at fair value	69,694		77,582
Fannie Mae [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	12,100	[1]	15,486	[1]
Gross unrealized gains	1,101		1,381
Gross unrealized losses - OTTI	(2)	[2]	(3)	[2]
Gross unrealized losses, other	(11)	[3]	(14)	[3]
Available-for-sale, at fair value	13,188		16,850
Freddie Mac [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	10,143	[1]	11,906	[1]
Gross unrealized gains	840		917
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross unrealized losses, other	0	[3]	0	[3]
Available-for-sale, at fair value	10,983		12,823
Ginnie Mae [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	710	[1]	775	[1]
Gross unrealized gains	119		127
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross unrealized losses, other	0	[3]	0	[3]
Available-for-sale, at fair value	829		902
Alt-A private-label securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	12,187	[1]	13,314	[1]
Gross unrealized gains	267		233
Gross unrealized losses - OTTI	(1,084)	[2]	(1,618)	[2]
Gross unrealized losses, other	(187)	[3]	(246)	[3]
Available-for-sale, at fair value	11,183		11,683
Subprime private-label securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	8,695	[1]	9,556	[1]
Gross unrealized gains	51		17
Gross unrealized losses - OTTI	(1,110)	[2]	(1,534)	[2]
Gross unrealized losses, other	(406)	[3]	(453)	[3]
Available-for-sale, at fair value	7,230		7,586
CMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	13,251	[1],[4]	13,949	[1],[4]
Gross unrealized gains	458		181
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross unrealized losses, other	(41)	[3]	(104)	[3]
Available-for-sale, at fair value	13,668		14,026
Deferred (gain) loss on discontinuation of fair value hedge	610		686
Mortgage revenue bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	9,295	[1]	10,172	[1]
Gross unrealized gains	175		202
Gross unrealized losses - OTTI	(54)	[2]	(56)	[2]
Gross unrealized losses, other	(59)	[3]	(64)	[3]
Available-for-sale, at fair value	9,357		10,254
Other mortgage-related securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	3,524	[1]	3,687	[1]
Gross unrealized gains	82		92
Gross unrealized losses - OTTI	(27)	[2]	(39)	[2]
Gross unrealized losses, other	(323)	[3]	(282)	[3]
Available-for-sale, at fair value	$ 3,256		$ 3,458

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

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

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

[4] Amortized cost includes $610 million and $686 million as of June 30, 2012 and December 31, 2011, respectively, of increase to the carrying amount from previous fair value hedge accounting.