Allowance for Loan Losses Rollforward by Segment (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Loan Losses [Roll Forward]
Beginning balance	$ (19,084)	$ (23,465)	$ (27,951)
Benefit (provision) for loan losses	2,987	1,941	1,759
Charge-offs	2,152	2,798	3,266
Recoveries	(240)	(329)	(449)
Other	(18)	(29)	(90)
Ending balance	(14,203)	(19,084)	(23,465)
Single-Family [Member]
Allowance for Loan Losses [Roll Forward]
Beginning balance	(18,849)	(23,283)	(27,709)
Benefit (provision) for loan losses	2,990	1,994	1,704
Charge-offs	2,148	2,795	3,254
Recoveries	(240)	(326)	(442)
Other	(18)	(29)	(90)
Ending balance	(13,969)	(18,849)	(23,283)
Multifamily [Member]
Allowance for Loan Losses [Roll Forward]
Beginning balance	(235)	(182)	(242)
Benefit (provision) for loan losses	(3)	(53)	55
Charge-offs	4	3	12
Recoveries	0	(3)	(7)
Ending balance	$ (234)	$ (235)	$ (182)

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

Amount of other addition (reduction) in allowance reserve for credit loss.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

The reserve to cover probable credit losses related to specifically identified fixed maturity real estate loans as well as probable credit losses inherent in the remainder of that loan portfolio.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82921503&loc=d3e21338-158488

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Amount of expense related to loss from loan transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

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