Mortgage Loans Loans in Mortgage Portfolio (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Loans in Mortgage Portfolio [Line Items]
Unpaid principal balance of mortgage loans	$ 3,011,280		$ 3,039,559
Cost basis and fair value adjustments, net	32,573		30,527
Allowance for loan losses for loans held for investment	(39,067)	(41,911)	(43,846)	(49,643)	(56,461)	(58,795)
Total mortgage loans	3,004,786		3,026,240
Single-Family [Member]
Loans in Mortgage Portfolio [Line Items]
Unpaid principal balance of mortgage loans	2,829,985		2,855,668
Multifamily [Member]
Loans in Mortgage Portfolio [Line Items]
Unpaid principal balance of mortgage loans	181,295		183,891
Fannie Mae [Member]
Loans in Mortgage Portfolio [Line Items]
Unpaid principal balance of mortgage loans	298,373		314,286
Cost basis and fair value adjustments, net	(13,164)		(13,778)
Allowance for loan losses for loans held for investment	(36,643)	(39,004)	(40,521)	(44,825)	(49,553)	(50,519)
Total mortgage loans	248,566		259,987
Fannie Mae [Member] | Single-Family [Member]
Loans in Mortgage Portfolio [Line Items]
Unpaid principal balance of mortgage loans	268,114		276,644
Fannie Mae [Member] | Multifamily [Member]
Loans in Mortgage Portfolio [Line Items]
Unpaid principal balance of mortgage loans	30,259		37,642
Consolidated Trusts [Member]
Loans in Mortgage Portfolio [Line Items]
Unpaid principal balance of mortgage loans	2,712,907		2,725,273
Cost basis and fair value adjustments, net	45,737		44,305
Allowance for loan losses for loans held for investment	(2,424)	(2,907)	(3,325)	(4,818)	(6,908)	(8,276)
Total mortgage loans	2,756,220		2,766,253
Consolidated Trusts [Member] | Single-Family [Member]
Loans in Mortgage Portfolio [Line Items]
Unpaid principal balance of mortgage loans	2,561,871		2,579,024
Consolidated Trusts [Member] | Multifamily [Member]
Loans in Mortgage Portfolio [Line Items]
Unpaid principal balance of mortgage loans	$ 151,036		$ 146,249