Investments in Securities Maturity Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Total amortized cost	$ 35,690	[1]	$ 61,766	[1]
Total fair value	38,171		63,181
One Year or Less, Amortized Cost	40
One Year or Less, Fair Value	42
After One Year through Five Years, Amortized Cost	2,346
After One Year through Five Years, Fair Value	2,473
After Five Years through Ten Years, Amortized Cost	1,707
After Five Years through Ten Years, Fair Value	1,798
After Ten Years, Amortized Cost	31,597
After Ten Years, Fair Value	33,858
Weighted average yield (percent)	5.42%	[2]
One Year or Less, Weighted Average Yield	5.88%	[2]
After One Year through Five Years, Weighted Average Yield	4.58%	[2]
After Five Years through Ten Years, Weighted Average Yield	5.94%	[2]
After Ten Years, Weighted Average Yield	5.45%	[2]
Fannie Mae [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Total amortized cost	6,227	[1]	9,580	[1]
Total fair value	6,573		10,435
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year through Five Years, Amortized Cost	322
After One Year through Five Years, Fair Value	341
After Five Years through Ten Years, Amortized Cost	376
After Five Years through Ten Years, Fair Value	404
After Ten Years, Amortized Cost	5,529
After Ten Years, Fair Value	5,828
Freddie Mac [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Total amortized cost	6,365	[1]	8,652	[1]
Total fair value	6,842		9,380
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year through Five Years, Amortized Cost	327
After One Year through Five Years, Fair Value	349
After Five Years through Ten Years, Amortized Cost	674
After Five Years through Ten Years, Fair Value	729
After Ten Years, Amortized Cost	5,364
After Ten Years, Fair Value	5,764
Ginnie Mae [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Total amortized cost	512	[1]	645	[1]
Total fair value	588		751
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year through Five Years, Amortized Cost	1
After One Year through Five Years, Fair Value	1
After Five Years through Ten Years, Amortized Cost	33
After Five Years through Ten Years, Fair Value	38
After Ten Years, Amortized Cost	478
After Ten Years, Fair Value	549
Alt-A private-label securities [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Total amortized cost	6,240	[1]	11,356	[1]
Total fair value	7,349		11,075
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year through Five Years, Amortized Cost	1
After One Year through Five Years, Fair Value	1
After Five Years through Ten Years, Amortized Cost	0
After Five Years through Ten Years, Fair Value	0
After Ten Years, Amortized Cost	6,239
After Ten Years, Fair Value	7,348
Subprime private-label securities [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Total amortized cost	6,232	[1]	8,137	[1]
Total fair value	7,068		7,447
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year through Five Years, Amortized Cost	0
After One Year through Five Years, Fair Value	0
After Five Years through Ten Years, Amortized Cost	0
After Five Years through Ten Years, Fair Value	0
After Ten Years, Amortized Cost	6,232
After Ten Years, Fair Value	7,068
CMBS [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Total amortized cost	1,526	[1]	12,284	[1]
Total fair value	1,606		13,097
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year through Five Years, Amortized Cost	1,435
After One Year through Five Years, Fair Value	1,513
After Five Years through Ten Years, Amortized Cost	0
After Five Years through Ten Years, Fair Value	0
After Ten Years, Amortized Cost	91
After Ten Years, Fair Value	93
Mortgage revenue bonds [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Total amortized cost	5,645	[1]	7,782	[1]
Total fair value	5,256		7,842
One Year or Less, Amortized Cost	40
One Year or Less, Fair Value	42
After One Year through Five Years, Amortized Cost	260
After One Year through Five Years, Fair Value	264
After Five Years through Ten Years, Amortized Cost	584
After Five Years through Ten Years, Fair Value	586
After Ten Years, Amortized Cost	4,761
After Ten Years, Fair Value	4,364
Other mortgage-related securities [Member]
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Total amortized cost	2,943	[1]	3,330	[1]
Total fair value	2,889		3,154
One Year or Less, Amortized Cost	0
One Year or Less, Fair Value	0
After One Year through Five Years, Amortized Cost	0
After One Year through Five Years, Fair Value	4
After Five Years through Ten Years, Amortized Cost	40
After Five Years through Ten Years, Fair Value	41
After Ten Years, Amortized Cost	2,903
After Ten Years, Fair Value	$ 2,844

[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 consolidated statements of operations and comprehensive income (loss).

[2] Yields are determined by dividing interest income (including amortization and accretion of premiums, discounts and other cost basis adjustments) by amortized cost balances as of year-end. Yields on tax-exempt obligations have been computed on a tax equivalent basis.