Fair Value Level 3 Valuation Inputs - Recurring (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	1,457	334
Mortgage commitment derivatives [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	255	265
Fannie Mae [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(6,403)	(1,308)
Consolidated Trusts [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment	15,629	14,268
Long-term debt	(19,483)	(14,976)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	3,030	2,774
Available-for-sale securities	15,080	19,012
Mortgage loans held for sale, at lower of cost or fair value	169	195
Mortgage loans held for investment	400,327	392,355
Total assets at fair value	419,874	415,630
Significant Unobservable Inputs (Level 3) [Member] \| Fannie Mae [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment	217,064	215,960
Long-term debt	(982)	(1,557)
Significant Unobservable Inputs (Level 3) [Member] \| Consolidated Trusts [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment	183,263	176,395
Long-term debt	(19,334)	(13,362)
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	3,030	2,774
Available-for-sale securities	15,080	19,012
Derivatives	45	(40)
Long-term debt	(890)	(1,473)
Total assets at fair value	20,125	24,555
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Agency [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	305	44
Available-for-sale securities	6	15
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Alt-A private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	597	618
Available-for-sale securities	3,140	3,791
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Subprime private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	1,307	1,448
Available-for-sale securities	5,240	7,068
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Mortgage revenue bonds [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	722	565
Available-for-sale securities	4,023	5,253
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Other [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	99	99
Available-for-sale securities	2,671	2,885
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Agency [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	153
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Agency [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Prepayment Speed (%)	100.00%
Spread (bps)	2.565%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Agency [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Prepayment Speed (%)	100.00%
Spread (bps)	3.508%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Agency [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Prepayment Speed (%)	100.00%
Spread (bps)	2.934%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Alt-A private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	290	60
Available-for-sale securities	322	139
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Alt-A private-label securities [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	8.30%	6.00%
Prepayment Speed (%)	2.90%	4.10%
Severity (%)	79.50%	76.10%
Spread (bps)	2.672%	4.143%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Alt-A private-label securities [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	9.10%	10.80%
Prepayment Speed (%)	3.20%	5.40%
Severity (%)	95.00%	92.70%
Spread (bps)	3.082%	4.217%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Alt-A private-label securities [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	8.50%	8.70%
Prepayment Speed (%)	3.10%	4.60%
Severity (%)	90.40%	83.10%
Spread (bps)	2.794%	4.175%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Alt-A private-label securities [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.20%	0.90%
Prepayment Speed (%)	0.20%	9.30%
Severity (%)	27.80%	53.70%
Spread (bps)	1.90%	3.00%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Alt-A private-label securities [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	13.10%	6.40%
Prepayment Speed (%)	20.50%	11.90%
Severity (%)	89.70%	82.60%
Spread (bps)	3.15%	4.00%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Alt-A private-label securities [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	4.60%	3.90%
Prepayment Speed (%)	8.20%	11.30%
Severity (%)	61.00%	68.80%
Spread (bps)	2.649%	3.493%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Subprime private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities		113
Available-for-sale securities	383	442
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Subprime private-label securities [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)		3.10%
Prepayment Speed (%)		1.80%
Severity (%)		75.00%
Spread (bps)		3.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Subprime private-label securities [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)		7.50%
Prepayment Speed (%)		2.50%
Severity (%)		87.20%
Spread (bps)		3.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Subprime private-label securities [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)		3.90%
Prepayment Speed (%)		2.00%
Severity (%)		75.80%
Spread (bps)		3.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Subprime private-label securities [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	2.10%	1.80%
Prepayment Speed (%)	1.50%	1.00%
Severity (%)	65.40%	65.00%
Spread (bps)	2.15%	2.75%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Subprime private-label securities [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	8.30%	11.00%
Prepayment Speed (%)	3.30%	9.40%
Severity (%)	95.00%	100.00%
Spread (bps)	2.62%	3.75%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Subprime private-label securities [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.50%	7.40%
Prepayment Speed (%)	2.10%	2.00%
Severity (%)	78.50%	82.20%
Spread (bps)	2.30%	3.152%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Mortgage revenue bonds [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	1,504	1,937
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Mortgage revenue bonds [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	(0.115%)	0.00%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Mortgage revenue bonds [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	3.615%	4.632%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Mortgage revenue bonds [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	0.527%	1.121%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Other [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	337
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Other [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	1.70%
Prepayment Speed (%)	3.00%
Severity (%)	4.00%
Spread (bps)	2.631%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Other [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.00%
Prepayment Speed (%)	9.30%
Severity (%)	94.60%
Spread (bps)	4.272%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor With Inputs [Member] \| Other [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	4.40%
Prepayment Speed (%)	3.80%
Severity (%)	69.60%
Spread (bps)	2.915%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor Without Inputs [Member] \| Alt-A private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	493	435
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor Without Inputs [Member] \| Subprime private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities		77
Available-for-sale securities		322
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor Without Inputs [Member] \| Mortgage revenue bonds [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	418	1,386
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Single Vendor Without Inputs [Member] \| Other [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities		122
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Agency [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	130
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Agency [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Prepayment Speed (%)	100.00%
Spread (bps)	1.846%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Agency [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Prepayment Speed (%)	100.00%
Spread (bps)	2.195%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Agency [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Prepayment Speed (%)	100.00%
Spread (bps)	1.975%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Alt-A private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	66	325
Available-for-sale securities	1,187	1,948
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Alt-A private-label securities [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.40%	6.90%
Prepayment Speed (%)	7.00%	1.90%
Severity (%)	48.80%	77.30%
Spread (bps)	2.648%	2.983%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Alt-A private-label securities [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.40%	10.40%
Prepayment Speed (%)	7.00%	2.50%
Severity (%)	48.80%	97.80%
Spread (bps)	2.648%	4.202%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Alt-A private-label securities [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.40%	8.90%
Prepayment Speed (%)	7.00%	2.20%
Severity (%)	48.80%	88.70%
Spread (bps)	2.648%	3.663%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Alt-A private-label securities [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.40%	0.10%
Prepayment Speed (%)	0.10%	0.10%
Severity (%)	0.20%	7.20%
Spread (bps)	1.838%	2.106%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Alt-A private-label securities [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	31.20%	10.30%
Prepayment Speed (%)	48.90%	32.90%
Severity (%)	95.00%	100.00%
Spread (bps)	2.40%	4.042%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Alt-A private-label securities [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.10%	3.50%
Prepayment Speed (%)	11.00%	9.90%
Severity (%)	59.60%	62.30%
Spread (bps)	2.367%	3.367%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Subprime private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	422	400
Available-for-sale securities	2,722	2,981
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Subprime private-label securities [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	3.50%	3.00%
Prepayment Speed (%)	1.40%	1.40%
Severity (%)	72.10%	50.40%
Spread (bps)	2.65%	3.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Subprime private-label securities [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	11.80%	9.20%
Prepayment Speed (%)	5.20%	2.20%
Severity (%)	95.00%	87.20%
Spread (bps)	2.65%	4.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Subprime private-label securities [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	7.20%	6.40%
Prepayment Speed (%)	2.80%	1.90%
Severity (%)	85.90%	74.40%
Spread (bps)	2.65%	3.53%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Subprime private-label securities [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	1.50%	0.00%
Prepayment Speed (%)	0.10%	0.30%
Severity (%)	1.50%	36.80%
Spread (bps)	1.55%	1.75%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Subprime private-label securities [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	37.40%	36.80%
Prepayment Speed (%)	17.70%	9.70%
Severity (%)	95.00%	100.00%
Spread (bps)	2.65%	3.75%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Subprime private-label securities [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	6.30%	7.40%
Prepayment Speed (%)	2.60%	2.30%
Severity (%)	84.40%	81.70%
Spread (bps)	2.20%	3.199%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Other [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	720	483
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Other [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.10%	0.10%
Prepayment Speed (%)	3.00%	3.00%
Severity (%)	0.40%	65.00%
Spread (bps)	2.15%	2.75%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Other [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	6.60%	5.00%
Prepayment Speed (%)	30.40%	11.40%
Severity (%)	95.00%	85.00%
Spread (bps)	4.814%	9.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus with Inputs [Member] \| Other [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	3.90%	5.00%
Prepayment Speed (%)	4.80%	3.00%
Severity (%)	62.40%	84.60%
Spread (bps)	3.206%	5.264%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus Without Inputs [Member] \| Alt-A private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	151	85
Available-for-sale securities	691	740
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus Without Inputs [Member] \| Subprime private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	549	808
Available-for-sale securities	1,755	2,442
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Consensus Without Inputs [Member] \| Other [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities		625
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Dealer Mark [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	150	32
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Dealer Mark [Member] \| Mortgage revenue bonds [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	161
Available-for-sale securities	510
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Dealer Mark [Member] \| Mortgage revenue bonds [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	2.881%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Dealer Mark [Member] \| Mortgage revenue bonds [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	2.881%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Dealer Mark [Member] \| Mortgage revenue bonds [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	2.881%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Dealer Mark [Member] \| Mortgage revenue bonds [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	2.228%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Dealer Mark [Member] \| Mortgage revenue bonds [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	3.221%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Dealer Mark [Member] \| Mortgage revenue bonds [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	2.659%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Dealer Mark [Member] \| Other [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	99
Available-for-sale securities	1,215
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Alt-A private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities		148
Available-for-sale securities	403	420
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Alt-A private-label securities [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)		4.00%
Prepayment Speed (%)		1.90%
Severity (%)		42.70%
Spread (bps)		3.254%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Alt-A private-label securities [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)		6.90%
Prepayment Speed (%)		3.40%
Severity (%)		77.30%
Spread (bps)		4.394%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Alt-A private-label securities [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)		6.50%
Prepayment Speed (%)		2.20%
Severity (%)		67.60%
Spread (bps)		4.186%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Alt-A private-label securities [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.00%	2.30%
Prepayment Speed (%)	0.50%	1.20%
Severity (%)	35.10%	45.20%
Spread (bps)	1.88%	2.202%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Alt-A private-label securities [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	11.50%	10.10%
Prepayment Speed (%)	8.40%	7.00%
Severity (%)	92.40%	79.50%
Spread (bps)	3.40%	5.00%
Significant Unobservable Inputs (Level 3) [Member] \| 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]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	7.00%	5.10%
Prepayment Speed (%)	3.40%	3.40%
Severity (%)	54.20%	60.50%
Spread (bps)	2.434%	3.813%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Subprime private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	290	50
Available-for-sale securities	317	816
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Subprime private-label securities [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	4.30%	6.90%
Prepayment Speed (%)	2.30%	0.10%
Severity (%)	62.20%	75.00%
Spread (bps)	2.65%	3.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Subprime private-label securities [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	6.20%	6.90%
Prepayment Speed (%)	4.20%	0.10%
Severity (%)	95.00%	75.00%
Spread (bps)	3.821%	3.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Subprime private-label securities [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.20%	6.90%
Prepayment Speed (%)	3.30%	0.10%
Severity (%)	73.80%	75.00%
Spread (bps)	2.837%	3.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Subprime private-label securities [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	3.00%	0.70%
Prepayment Speed (%)	1.10%	0.20%
Severity (%)	28.90%	43.80%
Spread (bps)	1.55%	1.75%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Subprime private-label securities [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	12.30%	7.60%
Prepayment Speed (%)	9.00%	12.50%
Severity (%)	91.80%	98.00%
Spread (bps)	8.95%	3.75%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Subprime private-label securities [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	7.00%	5.10%
Prepayment Speed (%)	4.10%	4.10%
Severity (%)	81.20%	79.50%
Spread (bps)	2.505%	2.924%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Mortgage revenue bonds [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	540	539
Available-for-sale securities	1,581	1,899
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Mortgage revenue bonds [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	0.06%	0.35%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Mortgage revenue bonds [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	3.18%	4.40%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Mortgage revenue bonds [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	2.63%	3.406%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Mortgage revenue bonds [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	(0.115%)	0.055%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Mortgage revenue bonds [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	6.202%	4.90%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Mortgage revenue bonds [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)	2.514%	3.10%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Other [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities		99
Available-for-sale securities		610
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Other [Member] \| Trading securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)		5.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Other [Member] \| Trading securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)		5.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Other [Member] \| Trading securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spread (bps)		5.25%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Other [Member] \| Available-for-sale Securities [Member] \| Minimum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)		5.00%
Prepayment Speed (%)		10.00%
Severity (%)		55.00%
Spread (bps)		3.00%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Other [Member] \| Available-for-sale Securities [Member] \| Maximum [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)		5.00%
Prepayment Speed (%)		10.00%
Severity (%)		55.00%
Spread (bps)		5.11%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Discounted Cash Flow with Inputs [Member] \| Other [Member] \| Available-for-sale Securities [Member] \| Weighted Average [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)		5.00%
Prepayment Speed (%)		10.00%
Severity (%)		55.00%
Spread (bps)		4.695%
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Internal Model [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	(107)	(64)
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Other Valuation Technique [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	2	(8)
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Other Valuation Technique [Member] \| Agency [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	22	44
Available-for-sale securities	6	15
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Other Valuation Technique [Member] \| Alt-A private-label securities [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	90
Available-for-sale securities	44	109
Significant Unobservable Inputs (Level 3) [Member] \| Recurring Fair Value Measurements [Member] \| Other Valuation Technique [Member] \| Subprime private-label securities [Member]

Fair Value Level 3 Valuation Inputs - Recurring (Details) (USD $)
In Millions, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Fair Value Inputs, Quantitative Information [Line Items]

Derivatives

1,457

334

Mortgage commitment derivatives [Member]

Fair Value Inputs, Quantitative Information [Line Items]

Derivatives

255