Commitments and Contingencies (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Value of the guarantees related to standby letters of credit		$ 57,361	$ 66,843
Maximum term of commitments to invest in mortgage loans		60 days
Other FHLBanks [Member]
Loss Contingencies [Line Items]
Par value of other FHLBanks' outstanding COs for which we are jointly and severally liable		$ 1,100,000,000	974,400,000
Maximum [Member]
Loss Contingencies [Line Items]
Standby letters of credit, original terms		20 years
Standby letters of credit, current terms		10 years
Standby letters of credit [Member]
Loss Contingencies [Line Items]
Off-balance-sheet Commitments Expiring Within One Year	[1],[2]	$ 7,468,699	7,484,754
Off-balance-sheet Commitments Expiring After One Year	[1],[2]	216,679	215,014
Total Off-balance Sheet Commitments	[1],[2]	7,685,378	7,699,768
Value of the guarantees related to standby letters of credit		1,500	1,700
Commitments of unused lines of credit - advances [Member]
Loss Contingencies [Line Items]
Off-balance-sheet Commitments Expiring Within One Year	[2],[3]	1,134,788	1,143,828
Off-balance-sheet Commitments Expiring After One Year	[2],[3]	0	0
Total Off-balance Sheet Commitments	[2],[3]	$ 1,134,788	1,143,828
Commitments of unused lines of credit - advances [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Period for commitments for unused line-of-credit advances		12 months
Commitments to make additional advances [Member]
Loss Contingencies [Line Items]
Off-balance-sheet Commitments Expiring Within One Year	[2]	$ 277,891	434,253
Off-balance-sheet Commitments Expiring After One Year	[2]	70,320	88,167
Total Off-balance Sheet Commitments	[2]	348,211	522,420
Unsettled CO bonds, at par [Member]
Loss Contingencies [Line Items]
Off-balance-sheet Commitments Expiring Within One Year	[2]	711,500	0
Off-balance-sheet Commitments Expiring After One Year	[2]	0	0
Total Off-balance Sheet Commitments	[2]	711,500	0
Unsettled CO discount notes, at par [Member]
Loss Contingencies [Line Items]
Off-balance-sheet Commitments Expiring Within One Year	[2]	1,227,230	500,000
Off-balance-sheet Commitments Expiring After One Year	[2]	0	0
Total Off-balance Sheet Commitments	[2]	1,227,230	500,000
Standby Letters of Credit Issuance Commitments [Member]
Loss Contingencies [Line Items]
Off-balance-sheet Commitments Expiring Within One Year		11,500	27,200
Off-balance-sheet Commitments Expiring After One Year		550	1,800
Mortgage Receivable [Member] | Commitments to invest in mortgage loans [Member]
Loss Contingencies [Line Items]
Off-balance-sheet Commitments Expiring Within One Year	[2]	98,765	49,911
Off-balance-sheet Commitments Expiring After One Year	[2]	0	0
Total Off-balance Sheet Commitments	[2]	$ 98,765	$ 49,911

[1] The amount of standby letters of credit outstanding excludes commitments to issue standby letters of credit that expire within one year. At March 31, 2020, and December 31, 2019, these amounts totaled $11.5 million and $27.2 million, respectively. Also excluded are commitments to issue standby letters of credit that expire after one year totaling $550 thousand and $1.8 million at March 31, 2020, and December 31, 2019, respectively.

[2] We have deemed it unnecessary to record any liability for credit losses on these agreements.

[3] Commitments for unused line-of-credit advances are generally for periods of up to 12 months. Since many of these commitments are not expected to be drawn upon, the total commitment amount does not necessarily indicate future liquidity requirements.