Consolidations and Transfers of Financial Assets Transfers of Financial Assets (Details) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			12 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Unconsolidated VIEs [Member]	Jun. 30, 2013 Unconsolidated VIEs [Member]	Jun. 30, 2014 Unconsolidated VIEs [Member]	Jun. 30, 2013 Unconsolidated VIEs [Member]	Jun. 30, 2014 Unconsolidated VIEs [Member] Fannie Mae Single-class MBS & Fannie Megas [Member]	Dec. 31, 2013 Unconsolidated VIEs [Member] Fannie Mae Single-class MBS & Fannie Megas [Member]	Jun. 30, 2014 Unconsolidated VIEs [Member] REMICS & SMBS [Member]		Dec. 31, 2013 Unconsolidated VIEs [Member] REMICS & SMBS [Member]
Transfers of Financial Assets [Line Items]
Unpaid principal balance portfolio securitizations	$ 36,400,000,000	$ 62,500,000,000	$ 68,900,000,000	$ 131,800,000,000
Unpaid principal balance									314,000,000	349,000,000	6,664,000,000	[1]	6,899,000,000	[1]
Fair value									350,000,000	383,000,000	7,878,000,000	[1]	7,959,000,000	[1]
Weighted-average coupon									6.19%	6.21%	5.30%	[1]	5.36%	[1]
Weighted-average loan age									7 years 11 months	7 years 5 months	5 years 8 months	[1]	5 years 5 months	[1]
Weighted-average maturity									21 years 0 months	21 years 6 months	11 years 1 month	[1]	12 years 7 months	[1]
Principal and interest received on retained interests					$ 373,000,000	$ 469,000,000	$ 713,000,000	$ 928,000,000

[1] Consists of real estate mortgage investment conduits (“REMICs”) and stripped mortgage-backed securities (“SMBS”).