Fair Value Nonrecurring Changes in Fair Value (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	$ 0		$ 0
Mortgage loans held for investment, at fair value	0		0
Total nonrecurring fair value measurements	52,104		52,939
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	164		185
Mortgage loans held for investment, at fair value	2,656,224		2,599,667
Total nonrecurring fair value measurements	2,734,213		2,694,859
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	210		195
Mortgage loans held for investment, at fair value	389,199		392,355
Total nonrecurring fair value measurements	409,718		415,630
Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	374		380
Mortgage loans held for investment, at fair value	3,045,423		2,992,022
Total nonrecurring fair value measurements	3,189,833		3,155,006
Fair Value, Measurements, Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	0		0
Other assets	0		0
Total nonrecurring fair value measurements	0		0
Fair Value, Measurements, Nonrecurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	87		101
Other assets	0		0
Total nonrecurring fair value measurements	87		101
Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	151		132
Other assets	39		121
Total nonrecurring fair value measurements	22,465		25,970
Fair Value, Measurements, Nonrecurring [Member] | Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	238		233
Other assets	39		121
Total nonrecurring fair value measurements	22,552		26,071
Fannie Mae [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	0		0
Fannie Mae [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	30,689		29,920
Fannie Mae [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	218,495		215,960
Fannie Mae [Member] | Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	249,184		245,880
Consolidated Trusts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	15,262		14,268
Consolidated Trusts [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	0		0
Consolidated Trusts [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	2,625,535		2,569,747
Consolidated Trusts [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	170,704		176,395
Consolidated Trusts [Member] | Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	2,796,239		2,746,142
Single-Family [Member] | Fair Value, Measurements, Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquired property, net	0		0
Single-Family [Member] | Fair Value, Measurements, Nonrecurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquired property, net	0		0
Single-Family [Member] | Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquired property, net	4,544		4,041
Single-Family [Member] | Fair Value, Measurements, Nonrecurring [Member] | Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquired property, net	4,544		4,041
Single-Family [Member] | Fannie Mae [Member] | Fair Value, Measurements, Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	0	[1]	0	[1]
Single-Family [Member] | Fannie Mae [Member] | Fair Value, Measurements, Nonrecurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	0	[1]	0	[1]
Single-Family [Member] | Fannie Mae [Member] | Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	16,771	[1]	19,966	[1]
Single-Family [Member] | Fannie Mae [Member] | Fair Value, Measurements, Nonrecurring [Member] | Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	16,771	[1]	19,966	[1]
Single-Family [Member] | Consolidated Trusts [Member] | Fair Value, Measurements, Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	0	[1]	0	[1]
Single-Family [Member] | Consolidated Trusts [Member] | Fair Value, Measurements, Nonrecurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	0	[1]	0	[1]
Single-Family [Member] | Consolidated Trusts [Member] | Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	56	[1]	79	[1]
Single-Family [Member] | Consolidated Trusts [Member] | Fair Value, Measurements, Nonrecurring [Member] | Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	56	[1]	79	[1]
Multifamily [Member] | Fair Value, Measurements, Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	0		0
Acquired property, net	0		0
Multifamily [Member] | Fair Value, Measurements, Nonrecurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	0		0
Acquired property, net	0		0
Multifamily [Member] | Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	747		1,533
Acquired property, net	157		98
Multifamily [Member] | Fair Value, Measurements, Nonrecurring [Member] | Estimated Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for investment, at fair value	747		1,533
Acquired property, net	$ 157		$ 98

[1] Excludes estimated recoveries from mortgage insurance proceeds.