Mortgage Loans Held for Portfolio MPF -Allowance Roll Forward Table (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2020		Sep. 30, 2019		Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance - MPF - Beginning of Period	$ 6,654				$ 6,654					$ 7,832
Adjustment for cumulative effect of accounting change - adoption of ASU 2016-13(1)	0	[1]	$ 0		(3,875)	[1]	$ 0
Allowance - MPF - End of Period	6,654				6,654					7,832
Credit Enhancement Fees Receivable	3,800				3,800
Impact on adoption -CECL	3,371,978		4,785,650		3,371,978		4,785,650		$ 3,818,842	4,472,836	$ 5,055,905	$ 5,376,294
Conventional MPF Loan [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance - MPF - Beginning of Period	6,654		8,260		6,654		8,260		5,900	7,832	8,493	7,309
(Charge-offs) Recoveries, net (2)	(584)		(172)	[2]	(428)	[2]	(85)	[2]
Provision for credit losses	1,338		(61)		3,125		1,036
Allowance - MPF - End of Period	6,654		$ 8,260		6,654		$ 8,260		$ 5,900	$ 7,832	$ 8,493	$ 7,309
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Impact on adoption -CECL	$ 113				$ 113

[1] As a result of adopting ASU 2016-13, the reduction to the Bank's ACL of $3.9 million was largely offset by a reversal of CE receivable of $3.8 million, resulting in a net impact of adoption of $0.1 million.

[2] Net charge-offs that the Bank does not expect to recover through CE receivable.