Derivative Instruments Derivatives 1 - Notional and FV Position (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
Asset Derivatives [Abstract]
Notional amount	$ 202,198,000,000		$ 245,573,000,000
Derivative asset, estimated fair value	1,256,000,000		2,073,000,000
Netting adjustment	(6,202,000,000)	[1]	(8,422,000,000)	[1]
Liability Derivatives [Abstract]
Notional amount	383,200,000,000		380,094,000,000
Derivative liability, estimated fair value	(443,000,000)		(1,469,000,000)
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	3,500,000,000		2,000,000,000
Cash collateral received for derivative instruments	685,000,000		1,000,000,000
Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	154,172,000,000		205,736,000,000
Derivative asset, estimated fair value	6,545,000,000		9,444,000,000
Accrued interest receivable, estimated fair value	807,000,000		786,000,000
Netting adjustment	(6,202,000,000)	[2]	(8,422,000,000)	[2]
Total net risk management derivatives	1,150,000,000		1,808,000,000
Liability Derivatives [Abstract]
Notional amount	327,064,000,000		346,994,000,000
Derivative liability, estimated fair value	(8,113,000,000)		(9,695,000,000)
Accrued interest payable, estimated fair value	(1,220,000,000)		(930,000,000)
Netting adjustment	9,040,000,000	[2]	9,370,000,000	[2]
Total net risk management derivatives	(293,000,000)		(1,255,000,000)
Mortgage commitment derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	48,026,000,000		39,837,000,000
Derivative asset, estimated fair value	106,000,000		265,000,000
Netting adjustment	0	[1]	0	[1]
Liability Derivatives [Abstract]
Notional amount	56,136,000,000		33,100,000,000
Derivative liability, estimated fair value	(150,000,000)		(214,000,000)
Netting adjustment	0	[1]	0	[1]
Pay-fixed Swap [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	72,309,000,000		68,637,000,000
Derivative asset, estimated fair value	2,387,000,000		5,378,000,000
Liability Derivatives [Abstract]
Notional amount	91,531,000,000		93,428,000,000
Derivative liability, estimated fair value	(4,963,000,000)		(4,759,000,000)
Receive-fixed Swap [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	56,477,000,000		67,527,000,000
Derivative asset, estimated fair value	3,753,000,000		3,320,000,000
Liability Derivatives [Abstract]
Notional amount	158,087,000,000		156,250,000,000
Derivative liability, estimated fair value	(2,229,000,000)		(3,813,000,000)
Basis Swap [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	2,544,000,000		27,014,000,000
Derivative asset, estimated fair value	87,000,000		36,000,000
Liability Derivatives [Abstract]
Notional amount	11,100,000,000		600,000,000
Derivative liability, estimated fair value	(2,000,000)		0
Foreign Currency Swap [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	358,000,000		389,000,000
Derivative asset, estimated fair value	131,000,000		120,000,000
Liability Derivatives [Abstract]
Notional amount	284,000,000		653,000,000
Derivative liability, estimated fair value	(24,000,000)		(38,000,000)
Pay-fixed Swaption [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	20,400,000,000		33,400,000,000
Derivative asset, estimated fair value	79,000,000		445,000,000
Liability Derivatives [Abstract]
Notional amount	31,525,000,000		48,025,000,000
Derivative liability, estimated fair value	(285,000,000)		(600,000,000)
Receive-fixed Swaption [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	2,000,000,000		8,000,000,000
Derivative asset, estimated fair value	82,000,000		117,000,000
Liability Derivatives [Abstract]
Notional amount	34,525,000,000		48,025,000,000
Derivative liability, estimated fair value	(609,000,000)		(484,000,000)
Other [Member] | Risk Management Derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	84,000,000	[3]	769,000,000	[3]
Derivative asset, estimated fair value	26,000,000	[3]	28,000,000	[3]
Liability Derivatives [Abstract]
Notional amount	12,000,000	[3]	13,000,000	[3]
Derivative liability, estimated fair value	(1,000,000)	[3]	(1,000,000)	[3]
Mortgage Commitments to Purchase Whole Loans [Member] | Mortgage commitment derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	4,009,000,000		1,138,000,000
Derivative asset, estimated fair value	9,000,000		1,000,000
Liability Derivatives [Abstract]
Notional amount	3,192,000,000		4,353,000,000
Derivative liability, estimated fair value	(6,000,000)		(31,000,000)
Forward Contracts to Purchase Mortgage-related Securities [Member] | Mortgage commitment derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	21,629,000,000		3,276,000,000
Derivative asset, estimated fair value	63,000,000		4,000,000
Liability Derivatives [Abstract]
Notional amount	16,822,000,000		20,861,000,000
Derivative liability, estimated fair value	(34,000,000)		(168,000,000)
Forward Contracts to Sell Mortgage-related Securities [Member] | Mortgage commitment derivatives [Member]
Asset Derivatives [Abstract]
Notional amount	22,388,000,000		35,423,000,000
Derivative asset, estimated fair value	34,000,000		260,000,000
Liability Derivatives [Abstract]
Notional amount	36,122,000,000		7,886,000,000
Derivative liability, estimated fair value	$ (110,000,000)		$ (15,000,000)

[1] Represents the effect of the right to offset under legally enforceable master netting arrangements to settle with the same counterparty on a net basis, including cash collateral posted and received and accrued interest.

[2] The netting adjustment for our risk management derivatives transactions represents the effect of the legal right to offset under legally enforceable master netting arrangements to settle with the same counterparty on a net basis, including cash collateral posted and received. Cash collateral posted was $3.5 billion and $2.0 billion as of September 30, 2014 and December 31, 2013, respectively. Cash collateral received was $685 million and $1.0 billion as of September 30, 2014 and December 31, 2013, respectively.

[3] Includes interest rate caps, futures, swap credit enhancements and mortgage insurance contracts that we account for as derivatives. The mortgage insurance contracts have payment provisions that are not based on a notional amount.