Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows provided by (used in) operating activities:
Net income	$ 2,463	$ 12,313	$ 10,955
Reconciliation of net income to net cash used in operating activities:
Amortization of cost basis adjustments	(6,641)	(6,821)	(6,298)
Benefit for credit losses	(2,041)	(2,155)	(795)
Valuation gains	(1,573)	(472)	(510)
Current and deferred federal income taxes	14,369	4,309	4,083
Net change in trading securities	4,511	(3,005)	(10,153)
Net gains related to the disposition of acquired property and preforeclosure sales, including credit enhancements	(2,426)	(3,124)	(3,055)
Other, net	(406)	(1,778)	(900)
Net cash provided by (used in) operating activities	8,256	(733)	(6,673)
Cash flows provided by investing activities:
Proceeds from maturities and paydowns of trading securities held for investment	1,206	1,840	768
Proceeds from sales of trading securities held for investment	241	1,618	1,104
Proceeds from maturities and paydowns of available-for-sale securities	2,009	2,927	4,394
Proceeds from sales of available-for-sale securities	1,990	11,378	8,249
Purchases of loans held for investment	(189,593)	(233,935)	(187,194)
Net change in restricted cash	8,803	(6,074)	1,663
Advances to lenders	(123,687)	(140,147)	(118,746)
Proceeds from disposition of acquired property and preforeclosure sales	12,221	16,115	20,757
Net change in federal funds sold and securities purchased under agreements to resell or similar arrangements	10,945	(3,065)	3,600
Other, net	641	116	527
Net cash provided by investing activities	193,211	224,979	248,324
Cash flows used in financing activities:
Payments of cash dividends on senior preferred stock to Treasury	(12,015)	(9,624)	(10,278)
Other, net	6	14	26
Net cash used in financing activities	(194,581)	(213,696)	(249,000)
Net increase (decrease) in cash and cash equivalents	6,886	10,550	(7,349)
Cash and cash equivalents at beginning of period	25,224	14,674	22,023
Cash and cash equivalents at end of period	32,110	25,224	14,674
Cash paid during the period for:
Interest	109,480	104,318	104,928
Income taxes	3,090	1,711	1,170
Non-cash activities:
Net mortgage loans acquired by assuming debt	258,312	275,710	220,168
Net transfers from mortgage loans of Fannie Mae to mortgage loans of consolidated trusts	193,809	223,705	175,104
Transfers from advances to lenders to loans held for investment of consolidated trusts	118,282	130,886	114,851
Net transfers from mortgage loans to acquired property	10,262	13,768	17,534
Transfers of mortgage loans from held for investment to held for sale	12,886	3,878	8,601
Fannie Mae [Member]
Cash flows provided by investing activities:
Proceeds from repayments of loans acquired as held for investment	22,557	25,294	25,776
Proceeds from sales of loans acquired as held for investment	10,241	5,222	3,196
Cash flows used in financing activities:
Proceeds from the issuance of debt	1,034,742	982,272	443,371
Payments to redeem debt	(1,086,470)	(1,043,108)	(518,575)
Consolidated Trusts [Member]
Cash flows provided by investing activities:
Proceeds from repayments of loans acquired as held for investment	435,637	543,690	484,230
Cash flows used in financing activities:
Proceeds from the issuance of debt	383,793	437,392	347,614
Payments to redeem debt	$ (514,637)	$ (580,642)	$ (511,158)