Investments in Securities Available-for-sale Securities 2 (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 65,425	[1]	$ 78,845	[1]
Gross unrealized gains	3,472		3,150
Gross unrealized losses - OTTI	(1,735)	[2]	(3,250)	[2]
Gross unrealized losses, other	(810)	[3]	(1,163)	[3]
Available-for-sale, at fair value	66,352		77,582
Fannie Mae [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	10,576	[1]	15,486	[1]
Gross unrealized gains	1,005		1,381
Gross unrealized losses - OTTI	(1)	[2]	(3)	[2]
Gross unrealized losses, other	(10)	[3]	(14)	[3]
Available-for-sale, at fair value	11,570		16,850
Freddie Mac [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	9,365	[1]	11,906	[1]
Gross unrealized gains	825		917
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross unrealized losses, other	0	[3]	0	[3]
Available-for-sale, at fair value	10,190		12,823
Ginnie Mae [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	676	[1]	775	[1]
Gross unrealized gains	116		127
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross unrealized losses, other	0	[3]	0	[3]
Available-for-sale, at fair value	792		902
Alt-A private-label securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	11,768	[1]	13,314	[1]
Gross unrealized gains	380		233
Gross unrealized losses - OTTI	(792)	[2]	(1,618)	[2]
Gross unrealized losses, other	(128)	[3]	(246)	[3]
Available-for-sale, at fair value	11,228		11,683
Subprime private-label securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	8,402	[1]	9,556	[1]
Gross unrealized gains	140		17
Gross unrealized losses - OTTI	(868)	[2]	(1,534)	[2]
Gross unrealized losses, other	(302)	[3]	(453)	[3]
Available-for-sale, at fair value	7,372		7,586
CMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	12,609	[1],[4]	13,949	[1],[4]
Gross unrealized gains	732		181
Gross unrealized losses - OTTI	0	[2]	0	[2]
Gross unrealized losses, other	(20)	[3]	(104)	[3]
Available-for-sale, at fair value	13,321		14,026
Deferred (gain) loss on discontinuation of fair value hedge	566		686
Mortgage revenue bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	8,604	[1]	10,172	[1]
Gross unrealized gains	176		202
Gross unrealized losses - OTTI	(52)	[2]	(56)	[2]
Gross unrealized losses, other	(55)	[3]	(64)	[3]
Available-for-sale, at fair value	8,673		10,254
Other mortgage-related securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	3,425	[1]	3,687	[1]
Gross unrealized gains	98		92
Gross unrealized losses - OTTI	(22)	[2]	(39)	[2]
Gross unrealized losses, other	(295)	[3]	(282)	[3]
Available-for-sale, at fair value	$ 3,206		$ 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 income (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 $566 million and $686 million as of September 30, 2012 and December 31, 2011, respectively, of increase to the carrying amount from previous fair value hedge accounting.