Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows provided by (used in) operating activities:
Net income	$ 14,160	$ 15,959	$ 2,463
Reconciliation of net income to net cash provided by operating activities:
Amortization of cost basis adjustments	(6,002)	(5,949)	(6,641)
Benefit for credit losses	(4,011)	(3,309)	(2,041)
Valuation gains	(1,809)	(911)	(1,573)
Current and deferred federal income taxes	1,517	3,680	14,369
Net gains related to the disposition of acquired property and preforeclosure sales, including credit enhancements	(917)	(1,785)	(2,426)
Other, net	(98)	440	(406)
Net change in trading securities	(1,630)	(5,454)	4,511
Interest Paid, Excluding Capitalized Interest, Operating Activities	(5,964)	(423)	(4,043)
Net cash provided by (used in) operating activities	(4,754)	2,248	4,213
Cash flows provided by investing activities:
Proceeds from maturities and paydowns of trading securities held for investment	58	182	1,206
Proceeds from sales of trading securities held for investment	49	96	241
Proceeds from maturities and paydowns of available-for-sale securities	469	695	2,009
Proceeds from sales of available-for-sale securities	537	760	1,990
Purchases of loans held for investment	(261,808)	(172,155)	(189,593)
Advances to lenders	(141,395)	(108,294)	(123,687)
Proceeds from disposition of acquired property and preforeclosure sales	7,425	9,321	12,221
Net change in federal funds sold and securities purchased under agreements to resell or similar arrangements	19,360	(13,468)	10,945
Other, net	(80)	78	641
Net cash provided by investing activities	207,052	150,853	184,408
Cash flows used in financing activities:
Payments of cash dividends on senior preferred stock to Treasury	(5,601)	(9,372)	(12,015)
Proceeds from senior preferred stock purchase agreement with Treasury	0	3,687	0
Other, net	480	63	6
Net cash used in financing activities	(190,314)	(163,938)	(190,538)
Net increase (decrease) in cash, cash equivalents and restricted cash	11,984	(10,837)	(1,917)
Cash, cash equivalents and restricted cash at beginning of period	49,423	60,260	62,177
Cash, cash equivalents and restricted cash at end of period	61,407	49,423	60,260
Cash paid during the period for:
Interest	121,542	110,415	109,480
Income taxes	1,900	460	3,090
Non-cash activities:
Net mortgage loans acquired by assuming debt	273,174	231,478	258,312
Net transfers from mortgage loans of Fannie Mae to mortgage loans of consolidated trusts	248,463	185,310	193,809
Transfers from advances to lenders to loans held for investment of consolidated trusts	128,272	102,865	118,282
Net transfers from mortgage loans to acquired property	6,681	8,131	10,262
Fannie Mae [Member]
Cash flows provided by investing activities:
Proceeds from repayments of loans acquired as held for investment	12,508	15,082	22,557
Proceeds from sales of loans acquired as held for investment	17,794	17,511	10,241
Cash flows used in financing activities:
Proceeds from the issuance of debt	789,572	789,355	1,034,742
Payments to redeem debt	(834,294)	(834,366)	(1,082,427)
Consolidated Trusts [Member]
Cash flows provided by investing activities:
Proceeds from repayments of loans acquired as held for investment	552,135	401,045	435,637
Cash flows used in financing activities:
Proceeds from the issuance of debt	435,235	357,846	383,793
Payments to redeem debt	$ (575,706)	$ (471,151)	$ (514,637)