Fair Value Level 3 Valuation Inputs (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 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	196		208
Trading securities	2,752		2,286
Available-for-sale securities	24,451		25,034
Mortgage loans held for investment, at amortized cost	449,318		466,594
Fannie Mae [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(770)		(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	223,862		232,170
Long-term debt	(992)		(1,056)
Consolidated Trusts [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	12,602		10,800
Long-term debt	(13,345)		(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	225,456		234,424
Long-term debt	(15,256)		(16,171)
Fair Value, Measurements, Nonrecurring [Member] | 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	124		135
Fair Value, Measurements, Nonrecurring [Member] | Consensus without Inputs [Member] | 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	124		135
Fair Value, Measurements, Nonrecurring [Member] | Multifamily [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	1,846		1,624
Fair Value, Measurements, Nonrecurring [Member] | Multifamily [Member] | Appraisals [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	186		194
Fair Value, Measurements, Nonrecurring [Member] | Multifamily [Member] | Other Valuation Technique [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	22		34
Fair Value, Measurements, Nonrecurring [Member] | Multifamily [Member] | Broker Price Opinions [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	407		395
Fair Value, Measurements, Nonrecurring [Member] | Multifamily [Member] | Asset Manager Estimate [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	1,231		1,001
Fair Value, Measurements, Nonrecurring [Member] | Fannie Mae [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	22,020	[1]	23,314	[1]
Fair Value, Measurements, Nonrecurring [Member] | Fannie Mae [Member] | Single-Family [Member] | Internal Model [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	22,020		23,314
Fair Value, Measurements, Nonrecurring [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	161	[1]	227	[1]
Fair Value, Measurements, Nonrecurring [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Internal Model [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at amortized cost	161		227
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	2,752		2,286
Available-for-sale securities	24,451		25,034
Derivatives	(7)		14
Long-term debt	(1,460)		(1,528)
Recurring Fair Value Measurements [Member] | Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			71	[2]
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	1,446		1,319
Available-for-sale securities	7,868		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	661		675
Available-for-sale securities	7,351		7,837
Recurring Fair Value Measurements [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	118		117
Available-for-sale securities	3,099		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	464		104
Available-for-sale securities	6,112		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	408		544
Available-for-sale securities	2,652		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 (%)	10.10%	[3]	10.90%	[3]
Prepayment Speed (%)	1.00%	[3]	0.30%	[3]
Severity (%)	66.50%	[3]	80.00%	[3]
Spreads (bps)	2.79%	[3]	4.27%	[3]
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 (%)	23.20%	[3]	23.00%	[3]
Prepayment Speed (%)	8.90%	[3]	7.90%	[3]
Severity (%)	88.40%	[3]	80.00%	[3]
Spreads (bps)	5.24%	[3]	6.57%	[3]
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 (%)	15.00%	[3]	16.00%	[3]
Prepayment Speed (%)	3.50%	[3]	2.60%	[3]
Severity (%)	79.30%	[3]	80.00%	[3]
Spreads (bps)	4.05%	[3]	4.885%	[3]
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%	[3]	0.00%	[3]
Prepayment Speed (%)	0.00%	[3]	0.00%	[3]
Severity (%)	50.60%	[3]	65.00%	[3]
Spreads (bps)	2.12%	[3]	3.25%	[3]
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 (%)	22.10%	[3]	27.40%	[3]
Prepayment Speed (%)	12.60%	[3]	14.40%	[3]
Severity (%)	100.00%	[3]	80.00%	[3]
Spreads (bps)	5.39%	[3]	6.60%	[3]
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 (%)	13.70%	[3]	15.40%	[3]
Prepayment Speed (%)	3.90%	[3]	3.00%	[3]
Severity (%)	78.20%	[3]	77.80%	[3]
Spreads (bps)	3.721%	[3]	4.937%	[3]
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	360		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 (%)	0.30%	[3]	0.00%	[3]
Prepayment Speed (%)	3.00%	[3]	1.00%	[3]
Severity (%)	85.00%	[3]	65.00%	[3]
Spreads (bps)	4.03%	[3]	4.50%	[3]
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 (%)	5.00%	[3]	5.00%	[3]
Prepayment Speed (%)	8.50%	[3]	14.10%	[3]
Severity (%)	100.00%	[3]	85.00%	[3]
Spreads (bps)	7.30%	[3]	7.29%	[3]
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 (%)	4.60%	[3]	4.70%	[3]
Prepayment Speed (%)	3.50%	[3]	3.60%	[3]
Severity (%)	86.30%	[3]	83.80%	[3]
Spreads (bps)	6.031%	[3]	5.858%	[3]
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	2,582		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%	[3]	0.00%	[3]
Prepayment Speed (%)	0.20%	[3]	0.20%	[3]
Severity (%)	1.20%	[3]	50.00%	[3]
Spreads (bps)	2.76%	[3]	3.00%	[3]
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 (%)	12.80%	[3]	17.70%	[3]
Prepayment Speed (%)	30.40%	[3]	41.30%	[3]
Severity (%)	100.00%	[3]	70.00%	[3]
Spreads (bps)	6.31%	[3]	6.34%	[3]
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 (%)	2.50%	[3]	3.60%	[3]
Prepayment Speed (%)	12.80%	[3]	10.00%	[3]
Severity (%)	49.90%	[3]	54.90%	[3]
Spreads (bps)	4.166%	[3]	4.29%	[3]
Recurring Fair Value Measurements [Member] | Dealer Mark [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	111		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	367		236
Available-for-sale securities	1,515		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 (%)	12.30%	[3]	14.10%	[3]
Prepayment Speed (%)	0.80%	[3]	3.40%	[3]
Severity (%)	29.40%	[3]	80.00%	[3]
Spreads (bps)	2.76%	[3]	4.22%	[3]
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 (%)	18.80%	[3]	20.40%	[3]
Prepayment Speed (%)	5.80%	[3]	8.30%	[3]
Severity (%)	80.00%	[3]	80.00%	[3]
Spreads (bps)	4.74%	[3]	6.37%	[3]
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 (%)	15.90%	[3]	18.70%	[3]
Prepayment Speed (%)	3.20%	[3]	5.60%	[3]
Severity (%)	60.00%	[3]	80.00%	[3]
Spreads (bps)	3.725%	[3]	5.648%	[3]
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 (%)	0.10%	[3]	0.00%	[3]
Prepayment Speed (%)	0.10%	[3]	0.00%	[3]
Severity (%)	15.70%	[3]	65.00%	[3]
Spreads (bps)	2.00%	[3]	2.99%	[3]
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 (%)	21.70%	[3]	24.30%	[3]
Prepayment Speed (%)	18.10%	[3]	10.90%	[3]
Severity (%)	100.00%	[3]	80.00%	[3]
Spreads (bps)	4.84%	[3]	6.54%	[3]
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 (%)	15.10%	[3]	15.70%	[3]
Prepayment Speed (%)	3.00%	[3]	2.90%	[3]
Severity (%)	77.50%	[3]	76.70%	[3]
Spreads (bps)	3.824%	[3]	5.27%	[3]
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	571		636
Available-for-sale securities	2,003		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)	2.60%	[3]	2.60%	[3]
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)	3.75%	[3]	3.75%	[3]
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)	3.261%	[3]	3.204%	[3]
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)	0.70%	[3]	0.77%	[3]
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)	3.79%	[3]	3.75%	[3]
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)	2.87%	[3]	2.977%	[3]
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	897		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 (%)	4.00%	[3]	4.00%	[3]
Prepayment Speed (%)	0.40%	[3]	0.20%	[3]
Severity (%)	50.00%	[3]	50.00%	[3]
Spreads (bps)	4.24%	[3]	4.31%	[3]
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 (%)	10.00%	[3]	10.00%	[3]
Prepayment Speed (%)	10.00%	[3]	10.00%	[3]
Severity (%)	85.00%	[3]	85.00%	[3]
Spreads (bps)	10.82%	[3]	11.54%	[3]
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%	[3]	5.00%	[3]
Prepayment Speed (%)	3.00%	[3]	3.00%	[3]
Severity (%)	84.80%	[3]	84.80%	[3]
Spreads (bps)	5.841%	[3]	5.886%	[3]
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	324		87
Available-for-sale securities	2,369		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 (%)	4.80%	[3]	5.70%	[3]
Prepayment Speed (%)	0.60%	[3]	0.60%	[3]
Severity (%)	42.20%	[3]	65.00%	[3]
Spreads (bps)	3.20%	[3]	5.26%	[3]
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 (%)	17.00%	[3]	17.60%	[3]
Prepayment Speed (%)	3.40%	[3]	4.00%	[3]
Severity (%)	99.00%	[3]	70.00%	[3]
Spreads (bps)	5.67%	[3]	6.12%	[3]
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 (%)	12.00%	[3]	12.50%	[3]
Prepayment Speed (%)	1.70%	[3]	1.70%	[3]
Severity (%)	80.90%	[3]	67.60%	[3]
Spreads (bps)	4.972%	[3]	5.67%	[3]
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%	[3]	0.00%	[3]
Prepayment Speed (%)	0.00%	[3]	0.00%	[3]
Severity (%)	6.70%	[3]	50.00%	[3]
Spreads (bps)	2.03%	[3]	2.88%	[3]
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 (%)	26.30%	[3]	23.60%	[3]
Prepayment Speed (%)	20.70%	[3]	20.80%	[3]
Severity (%)	96.30%	[3]	70.00%	[3]
Spreads (bps)	5.50%	[3]	6.43%	[3]
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 (%)	6.50%	[3]	6.40%	[3]
Prepayment Speed (%)	6.70%	[3]	7.40%	[3]
Severity (%)	56.80%	[3]	57.20%	[3]
Spreads (bps)	3.835%	[3]	4.428%	[3]
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]
Trading securities	90
Available-for-sale securities	3,846
Recurring Fair Value Measurements [Member] | Single Vendor 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)	0.70%	[3]
Recurring Fair Value Measurements [Member] | Single Vendor 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)	2.60%	[3]
Recurring Fair Value Measurements [Member] | Single Vendor 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)	2.239%	[3]
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)	0.48%	[3]
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)	4.69%	[3]
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)	1.294%	[3]
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	122
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 (%)	5.10%	[3]
Prepayment Speed (%)	2.90%	[3]
Severity (%)	63.80%	[3]
Spreads (bps)	4.53%	[3]
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 (%)	12.80%	[3]
Prepayment Speed (%)	4.40%	[3]
Severity (%)	83.10%	[3]
Spreads (bps)	4.99%	[3]
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 (%)	10.60%	[3]
Prepayment Speed (%)	3.40%	[3]
Severity (%)	77.80%	[3]
Spreads (bps)	4.862%	[3]
Recurring Fair Value Measurements [Member] | Internal Model [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	(118)		(130)
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	21	[2]	39	[2]
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	68		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]
Available-for-sale securities	136		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	118		117
Available-for-sale securities	686		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			17
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	63	[2]	44	[2]
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	462		355
Available-for-sale securities	3,309		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	1,156		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	18
Available-for-sale securities	1,089		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	[2]
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	209		184
Available-for-sale securities	324
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	1,366		5,721
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	72		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	(383)		(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	(383)		(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	(383)		(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	2,882		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	(204)		(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 (%)	0.00%	[3]	0.00%	[3]
Prepayment Speed (%)	0.00%	[3]	1.70%	[3]
Severity (%)	50.00%	[3]	65.00%	[3]
Spreads (bps)	3.73%	[3]	4.68%	[3]
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 (%)	8.10%	[3]	9.00%	[3]
Prepayment Speed (%)	14.30%	[3]	14.40%	[3]
Severity (%)	94.30%	[3]	70.00%	[3]
Spreads (bps)	7.15%	[3]	8.51%	[3]
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 (%)	6.50%	[3]	6.20%	[3]
Prepayment Speed (%)	8.10%	[3]	10.90%	[3]
Severity (%)	67.80%	[3]	67.50%	[3]
Spreads (bps)	5.177%	[3]	5.843%	[3]
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	(312)		(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 (%)	4.00%	[3]	0.00%	[3]
Prepayment Speed (%)	0.00%	[3]	0.00%	[3]
Severity (%)	50.00%	[3]	50.00%	[3]
Spreads (bps)	0.821%	[3]	0.98%	[3]
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 (%)	10.00%	[3]	10.00%	[3]
Prepayment Speed (%)	100.00%	[3]	100.00%	[3]
Severity (%)	89.70%	[3]	70.00%	[3]
Spreads (bps)	8.92%	[3]	10.30%	[3]
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 (%)	6.30%	[3]	5.80%	[3]
Prepayment Speed (%)	47.80%	[3]	36.90%	[3]
Severity (%)	79.00%	[3]	63.40%	[3]
Spreads (bps)	4.248%	[3]	3.314%	[3]
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	(97)
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	(464)		(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			(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	2,690		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	1,910		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%	[3]	0.10%	[3]
Prepayment Speed (%)	3.40%	[3]	4.40%	[3]
Severity (%)	6.10%	[3]	5.60%	[3]
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 (%)	92.00%	[3]	99.30%	[3]
Prepayment Speed (%)	44.80%	[3]	92.00%	[3]
Severity (%)	96.90%	[3]	97.30%	[3]
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 (%)	20.90%	[3]	18.40%	[3]
Prepayment Speed (%)	17.20%	[3]	19.40%	[3]
Severity (%)	32.50%	[3]	33.30%	[3]
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	237		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 (%)	0.00%	[3]	0.00%	[3]
Prepayment Speed (%)	0.00%	[3]	1.70%	[3]
Severity (%)	50.90%	[3]	65.00%	[3]
Spreads (bps)	3.73%	[3]	4.68%	[3]
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 (%)	8.10%	[3]	9.00%	[3]
Prepayment Speed (%)	14.30%	[3]	14.40%	[3]
Severity (%)	94.30%	[3]	70.00%	[3]
Spreads (bps)	7.15%	[3]	8.51%	[3]
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 (%)	6.40%	[3]	6.40%	[3]
Prepayment Speed (%)	7.60%	[3]	10.40%	[3]
Severity (%)	72.60%	[3]	67.10%	[3]
Spreads (bps)	4.979%	[3]	5.679%	[3]
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	141		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 (%)	4.30%	[3]	0.00%	[3]
Prepayment Speed (%)	0.30%	[3]	1.70%	[3]
Severity (%)	57.00%	[3]	65.00%	[3]
Spreads (bps)	3.26%	[3]	5.07%	[3]
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 (%)	6.80%	[3]	8.50%	[3]
Prepayment Speed (%)	14.30%	[3]	14.40%	[3]
Severity (%)	89.70%	[3]	70.00%	[3]
Spreads (bps)	8.92%	[3]	10.30%	[3]
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 (%)	6.40%	[3]	6.00%	[3]
Prepayment Speed (%)	4.20%	[3]	5.30%	[3]
Severity (%)	81.90%	[3]	65.00%	[3]
Spreads (bps)	6.346%	[3]	7.334%	[3]
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	402		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	192		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)	0.77%	[3]	0.77%	[3]
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)	3.404%	[3]	3.634%	[3]
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)	1.49%	[3]	1.545%	[3]

[1] Excludes estimated recoveries from mortgage insurance proceeds.

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

[3] 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.