Fair Value Level 3 Valuation Inputs (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	$ 267		$ 208
Trading securities	2,959		2,286
Available-for-sale securities	24,340		25,034
Mortgage loans held for investment, at amortized cost	406,415		466,594
Assets, Fair Value Disclosure	435,326		495,561
Fannie Mae [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(720)		(793)
Fannie Mae [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	225,059		232,170
Long-term debt	(944)		(1,056)
Consolidated Trusts [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	13,770		10,800
Long-term debt	(14,601)		(11,647)
Consolidated Trusts [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	181,356		234,424
Long-term debt	(14,554)		(16,171)
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	2,959		2,286
Available-for-sale securities	24,340		25,034
Derivatives	(49)		14
Long-term debt	(1,414)		(1,528)
Assets, Fair Value Disclosure	30,365		30,129
Recurring Fair Value Measurements [Member] | Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			71	[1]
Recurring Fair Value Measurements [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	1,488		1,319
Available-for-sale securities	7,862		7,447
Recurring Fair Value Measurements [Member] | Mortgage revenue bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	603		675
Available-for-sale securities	6,400		7,837
Recurring Fair Value Measurements [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	109		117
Available-for-sale securities	3,051		3,147
Recurring Fair Value Measurements [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	703		104
Available-for-sale securities	7,008		6,564
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	632		544
Available-for-sale securities	2,882		3,333
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	9.00%	[2]	10.90%	[2]
Prepayment Speed (%)	0.70%	[2]	0.30%	[2]
Severity (%)	64.60%	[2]	80.00%	[2]
Spreads (bps)	2.55%	[2]	4.27%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	18.60%	[2]	23.00%	[2]
Prepayment Speed (%)	8.00%	[2]	7.90%	[2]
Severity (%)	88.30%	[2]	80.00%	[2]
Spreads (bps)	5.38%	[2]	6.57%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	14.20%	[2]	16.00%	[2]
Prepayment Speed (%)	5.10%	[2]	2.60%	[2]
Severity (%)	78.60%	[2]	80.00%	[2]
Spreads (bps)	3.291%	[2]	4.885%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.00%	[2]	0.00%	[2]
Prepayment Speed (%)	0.00%	[2]	0.00%	[2]
Severity (%)	24.30%	[2]	65.00%	[2]
Spreads (bps)	1.44%	[2]	3.25%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	27.40%	[2]	27.40%	[2]
Prepayment Speed (%)	27.40%	[2]	14.40%	[2]
Severity (%)	97.70%	[2]	80.00%	[2]
Spreads (bps)	5.69%	[2]	6.60%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	13.10%	[2]	15.40%	[2]
Prepayment Speed (%)	4.60%	[2]	3.00%	[2]
Severity (%)	75.60%	[2]	77.80%	[2]
Spreads (bps)	3.193%	[2]	4.937%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	122		534
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.00%	[2]	0.00%	[2]
Prepayment Speed (%)	2.30%	[2]	1.00%	[2]
Severity (%)	0.00%	[2]	65.00%	[2]
Spreads (bps)	2.80%	[2]	4.50%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	12.60%	[2]	5.00%	[2]
Prepayment Speed (%)	13.70%	[2]	14.10%	[2]
Severity (%)	100.00%	[2]	85.00%	[2]
Spreads (bps)	9.52%	[2]	7.29%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	4.00%	[2]	4.70%	[2]
Prepayment Speed (%)	5.50%	[2]	3.60%	[2]
Severity (%)	79.40%	[2]	83.80%	[2]
Spreads (bps)	4.885%	[2]	5.858%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	2,621		2,285
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.00%	[2]	0.00%	[2]
Prepayment Speed (%)	0.00%	[2]	0.20%	[2]
Severity (%)	3.70%	[2]	50.00%	[2]
Spreads (bps)	1.77%	[2]	3.00%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	16.20%	[2]	17.70%	[2]
Prepayment Speed (%)	35.50%	[2]	41.30%	[2]
Severity (%)	100.00%	[2]	70.00%	[2]
Spreads (bps)	5.97%	[2]	6.34%	[2]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	3.50%	[2]	3.60%	[2]
Prepayment Speed (%)	13.10%	[2]	10.00%	[2]
Severity (%)	55.70%	[2]	54.90%	[2]
Spreads (bps)	4.513%	[2]	4.29%	[2]
Recurring Fair Value Measurements [Member] | Dealer Mark [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	66		144
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	423		236
Available-for-sale securities	852		1,710
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	9.80%	[2]	14.10%	[2]
Prepayment Speed (%)	2.10%	[2]	3.40%	[2]
Severity (%)	38.70%	[2]	80.00%	[2]
Spreads (bps)	2.55%	[2]	4.22%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	22.30%	[2]	20.40%	[2]
Prepayment Speed (%)	5.10%	[2]	8.30%	[2]
Severity (%)	99.00%	[2]	80.00%	[2]
Spreads (bps)	4.08%	[2]	6.37%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	13.60%	[2]	18.70%	[2]
Prepayment Speed (%)	3.40%	[2]	5.60%	[2]
Severity (%)	69.70%	[2]	80.00%	[2]
Spreads (bps)	3.108%	[2]	5.648%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.40%	[2]	0.00%	[2]
Prepayment Speed (%)	0.60%	[2]	0.00%	[2]
Severity (%)	60.20%	[2]	65.00%	[2]
Spreads (bps)	0.65%	[2]	2.99%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	24.30%	[2]	24.30%	[2]
Prepayment Speed (%)	14.90%	[2]	10.90%	[2]
Severity (%)	100.00%	[2]	80.00%	[2]
Spreads (bps)	4.50%	[2]	6.54%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	16.40%	[2]	15.70%	[2]
Prepayment Speed (%)	3.50%	[2]	2.90%	[2]
Severity (%)	77.50%	[2]	76.70%	[2]
Spreads (bps)	3.10%	[2]	5.27%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	578		636
Available-for-sale securities	1,846		1,911
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Trading securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	2.21%	[2]	2.60%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Trading securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	4.15%	[2]	3.75%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Trading securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	3.581%	[2]	3.204%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	0.58%	[2]	0.77%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	5.55%	[2]	3.75%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	3.279%	[2]	2.977%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	322		916
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.00%	[2]	4.00%	[2]
Prepayment Speed (%)	3.00%	[2]	0.20%	[2]
Severity (%)	85.00%	[2]	50.00%	[2]
Spreads (bps)	3.90%	[2]	4.31%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.00%	[2]	10.00%	[2]
Prepayment Speed (%)	3.00%	[2]	10.00%	[2]
Severity (%)	85.00%	[2]	85.00%	[2]
Spreads (bps)	5.63%	[2]	11.54%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.00%	[2]	5.00%	[2]
Prepayment Speed (%)	3.00%	[2]	3.00%	[2]
Severity (%)	85.00%	[2]	84.80%	[2]
Spreads (bps)	4.114%	[2]	5.886%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	139		87
Available-for-sale securities	1,174		3,003
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	11.20%	[2]	5.70%	[2]
Prepayment Speed (%)	0.40%	[2]	0.60%	[2]
Severity (%)	50.00%	[2]	65.00%	[2]
Spreads (bps)	3.13%	[2]	5.26%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	13.40%	[2]	17.60%	[2]
Prepayment Speed (%)	4.30%	[2]	4.00%	[2]
Severity (%)	77.60%	[2]	70.00%	[2]
Spreads (bps)	3.54%	[2]	6.12%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	12.70%	[2]	12.50%	[2]
Prepayment Speed (%)	3.00%	[2]	1.70%	[2]
Severity (%)	68.50%	[2]	67.60%	[2]
Spreads (bps)	3.405%	[2]	5.67%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.00%	[2]	0.00%	[2]
Prepayment Speed (%)	0.00%	[2]	0.00%	[2]
Severity (%)	35.70%	[2]	50.00%	[2]
Spreads (bps)	1.11%	[2]	2.88%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	20.00%	[2]	23.60%	[2]
Prepayment Speed (%)	16.20%	[2]	20.80%	[2]
Severity (%)	97.60%	[2]	70.00%	[2]
Spreads (bps)	4.79%	[2]	6.43%	[2]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	6.70%	[2]	6.40%	[2]
Prepayment Speed (%)	4.80%	[2]	7.40%	[2]
Severity (%)	58.10%	[2]	57.20%	[2]
Spreads (bps)	2.943%	[2]	4.428%	[2]
Recurring Fair Value Measurements [Member] | Internal Model [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	(83)		(130)
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	(32)
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	56	[1]
Available-for-sale securities	19	[1]	39	[1]
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	373		78
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Mortgage revenue bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	25
Available-for-sale securities	127		205
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	109		117
Available-for-sale securities	1,932		688
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	73		17
Available-for-sale securities	1,352
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	94
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	9.00%	[2]
Prepayment Speed (%)	5.00%	[2]
Severity (%)	65.00%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	18.70%	[2]
Prepayment Speed (%)	7.20%	[2]
Severity (%)	94.30%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	18.60%	[2]
Prepayment Speed (%)	7.10%	[2]
Severity (%)	94.00%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Mortgage revenue bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	3,092
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	0.47%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	5.03%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	1.226%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	127
Available-for-sale securities	137
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	12.40%	[2]
Prepayment Speed (%)	1.40%	[2]
Severity (%)	71.70%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	12.40%	[2]
Prepayment Speed (%)	1.40%	[2]
Severity (%)	71.70%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	12.40%	[2]
Prepayment Speed (%)	1.40%	[2]
Severity (%)	71.70%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	7.50%	[2]
Prepayment Speed (%)	0.20%	[2]
Severity (%)	35.50%	[2]
Spreads (bps)	3.45%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	14.40%	[2]
Prepayment Speed (%)	7.00%	[2]
Severity (%)	86.20%	[2]
Spreads (bps)	3.45%	[2]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	9.70%	[2]
Prepayment Speed (%)	3.40%	[2]
Severity (%)	76.50%	[2]
Spreads (bps)	3.45%	[2]
Recurring Fair Value Measurements [Member] | Consensus without Inputs [Member] | Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			44	[1]
Recurring Fair Value Measurements [Member] | Consensus without Inputs [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	433		355
Available-for-sale securities	3,661		2,326
Recurring Fair Value Measurements [Member] | Consensus without Inputs [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	659		1,009
Recurring Fair Value Measurements [Member] | Consensus without Inputs [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	364
Available-for-sale securities	1,561		1,231
Recurring Fair Value Measurements [Member] | Single Vendor without Inputs [Member] | Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			27	[1]
Recurring Fair Value Measurements [Member] | Single Vendor without Inputs [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			184
Recurring Fair Value Measurements [Member] | Single Vendor without Inputs [Member] | Mortgage revenue bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			39
Available-for-sale securities	1,335		5,721
Recurring Fair Value Measurements [Member] | Single Vendor without Inputs [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	16
Recurring Fair Value Measurements [Member] | Single Vendor without Inputs [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	163		45
Recurring Fair Value Measurements [Member] | Fannie Mae [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(337)		(400)
Recurring Fair Value Measurements [Member] | Fannie Mae [Member] | Senior Floating [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(337)		(400)
Recurring Fair Value Measurements [Member] | Fannie Mae [Member] | Discounted Cash Flow without Inputs [Member] | Senior Floating [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(337)		(400)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	2,961		2,634
Long-term debt	(1,077)		(1,128)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Consensus with Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(346)		(271)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Consensus with Inputs [Member] | Long-term debt [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.60%	[2]	0.00%	[2]
Prepayment Speed (%)	0.00%	[2]	1.70%	[2]
Severity (%)	39.90%	[2]	65.00%	[2]
Spreads (bps)	1.67%	[2]	4.68%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Consensus with Inputs [Member] | Long-term debt [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	15.60%	[2]	9.00%	[2]
Prepayment Speed (%)	16.10%	[2]	14.40%	[2]
Severity (%)	100.00%	[2]	70.00%	[2]
Spreads (bps)	9.31%	[2]	8.51%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Consensus with Inputs [Member] | Long-term debt [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.80%	[2]	6.20%	[2]
Prepayment Speed (%)	7.80%	[2]	10.90%	[2]
Severity (%)	59.20%	[2]	67.50%	[2]
Spreads (bps)	4.261%	[2]	5.843%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Discounted Cash Flow with Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(105)		(330)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Discounted Cash Flow with Inputs [Member] | Long-term debt [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	11.80%	[2]	0.00%	[2]
Prepayment Speed (%)	2.50%	[2]	0.00%	[2]
Severity (%)	99.40%	[2]	50.00%	[2]
Spreads (bps)	0.92%	[2]	0.98%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Discounted Cash Flow with Inputs [Member] | Long-term debt [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	11.80%	[2]	10.00%	[2]
Prepayment Speed (%)	100.00%	[2]	100.00%	[2]
Severity (%)	99.40%	[2]	70.00%	[2]
Spreads (bps)	7.52%	[2]	10.30%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Discounted Cash Flow with Inputs [Member] | Long-term debt [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	11.80%	[2]	5.80%	[2]
Prepayment Speed (%)	94.30%	[2]	36.90%	[2]
Severity (%)	99.40%	[2]	63.40%	[2]
Spreads (bps)	1.866%	[2]	3.314%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Other Valuation Technique [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(50)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Consensus without Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(508)		(370)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single Vendor without Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(68)		(157)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	2,772		2,459
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Build-Up [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	1,969		1,698
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Build-Up [Member] | Mortgage Loans [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.10%	[2]	0.10%	[2]
Prepayment Speed (%)	3.00%	[2]	4.40%	[2]
Severity (%)	6.10%	[2]	5.60%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Build-Up [Member] | Mortgage Loans [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	97.40%	[2]	99.30%	[2]
Prepayment Speed (%)	42.50%	[2]	92.00%	[2]
Severity (%)	96.10%	[2]	97.30%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Build-Up [Member] | Mortgage Loans [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	19.20%	[2]	18.40%	[2]
Prepayment Speed (%)	15.10%	[2]	19.40%	[2]
Severity (%)	29.90%	[2]	33.30%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Consensus with Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	380		302
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Consensus with Inputs [Member] | Mortgage Loans [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.60%	[2]	0.00%	[2]
Prepayment Speed (%)	0.00%	[2]	1.70%	[2]
Severity (%)	39.90%	[2]	65.00%	[2]
Spreads (bps)	1.67%	[2]	4.68%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Consensus with Inputs [Member] | Mortgage Loans [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	15.60%	[2]	9.00%	[2]
Prepayment Speed (%)	16.10%	[2]	14.40%	[2]
Severity (%)	100.00%	[2]	70.00%	[2]
Spreads (bps)	9.31%	[2]	8.51%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Consensus with Inputs [Member] | Mortgage Loans [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	6.10%	[2]	6.40%	[2]
Prepayment Speed (%)	7.20%	[2]	10.40%	[2]
Severity (%)	61.60%	[2]	67.10%	[2]
Spreads (bps)	4.045%	[2]	5.679%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Discounted Cash Flow with Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	3		106
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage Loans [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	11.80%	[2]	0.00%	[2]
Prepayment Speed (%)	2.50%	[2]	1.70%	[2]
Severity (%)	99.40%	[2]	65.00%	[2]
Spreads (bps)	7.52%	[2]	5.07%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage Loans [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	11.80%	[2]	8.50%	[2]
Prepayment Speed (%)	2.50%	[2]	14.40%	[2]
Severity (%)	99.40%	[2]	70.00%	[2]
Spreads (bps)	7.52%	[2]	10.30%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage Loans [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	11.80%	[2]	6.00%	[2]
Prepayment Speed (%)	2.50%	[2]	5.30%	[2]
Severity (%)	99.40%	[2]	65.00%	[2]
Spreads (bps)	7.52%	[2]	7.334%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Consensus without Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	420		303
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Single Vendor without Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost			50
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Multifamily [Member] | Build-Up [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	$ 189		$ 175
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Multifamily [Member] | Build-Up [Member] | Mortgage Loans [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	0.80%	[2]	0.77%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Multifamily [Member] | Build-Up [Member] | Mortgage Loans [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	2.854%	[2]	3.634%	[2]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Multifamily [Member] | Build-Up [Member] | Mortgage Loans [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	1.334%	[2]	1.545%	[2]

[1] Includes Fannie Mae, Freddie Mac and Ginnie Mae securities.

[2] Valuation techniques for which no unobservable inputs are disclosed generally reflect the use of third-party pricing services or dealers, and the range of unobservable inputs applied by these sources is not readily available or cannot be reasonably estimated. Where we have disclosed unobservable inputs for consensus and single vendor techniques, those inputs are based on our validations performed at the security level using discounted cash flows.