Advances (Portfolio by Year of Contractual Maturity) (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019
Federal Home Loan Bank, Advances, Weighted Average Interest Rate, Rolling Year [Abstract]
Due in 1 year or less		0.78%	1.97%
Due after 1 year through 2 years		2.20%	2.31%
Due after 2 years through 3 years		2.34%	2.52%
Due after 3 years through 4 years		1.95%	2.50%
Due after 4 years through 5 years		1.99%	2.10%
Thereafter		2.57%	2.76%
Total par value, Weighted Average Interest Rate		1.31%	2.12%
Federal Home Loan Bank, Advances, Maturity, Rolling Year, Par Value [Abstract]
Due in 1 year or less		$ 22,167,019	$ 41,261,372
Due after 1 year through 2 years		7,958,117	15,285,269
Due after 2 years through 3 years		2,686,918	6,065,460
Due after 3 years through 4 years		1,226,558	1,305,453
Due after 4 years through 5 years		1,235,193	869,892
Thereafter		208,778	651,673
Total Par Value		35,482,583	65,439,119
Deferred prepayment fees		(2,744)	(1,814)
Hedging adjustments		361,197	172,770
Total book value	[1]	35,841,036	65,610,075
FederalHomeLoanBankAdvancesReceivable [Member]
Federal Home Loan Bank, Advances [Line Items]
Accrued Interest - Advances		$ 49,200	$ 119,700

[1] Amounts exclude accrued interest receivable of $49.2 million and $119.7 million at September 30, 2020 and December 31, 2019