Estimated Fair Values (Fair Value Measured on Recurring and Nonrecurring Basis) (Details) - USD ($)		Sep. 30, 2020		Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		$ 1,287,548,000		$ 3,631,650,000
AFS Securities		10,153,022,000		11,097,769,000
Derivative assets		160,986,000		140,251,000
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	[1],[2]	153,534,000		124,050,000
Derivative liabilities		1,751,000		3,024,000
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[1],[2]	(3,578,000)		(5,845,000)
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		0		0
AFS Securities		0		0
Derivative assets		0		0
Derivative liabilities		0		0
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		1,287,548,000		3,631,650,000
AFS Securities		9,885,398,000		10,771,623,000
Derivative assets		7,452,000		16,201,000
Derivative liabilities		5,329,000		8,869,000
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		0		0
AFS Securities		267,624,000		326,146,000
Derivative assets		0		0
Derivative liabilities		0		0
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	[3]	153,534,000		124,050,000
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[4]	(3,578,000)	[2]	(5,845,000)	[3]
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		0		0
AFS Securities		0		0
Derivative assets		0		0
Derivative liabilities		0
Total assets at fair value		0		0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		1,287,548,000		3,631,650,000
AFS Securities		9,885,398,000		10,771,623,000
Derivative assets		7,452,000		16,201,000
Derivative liabilities	[4]	5,329,000		8,869,000
Total assets at fair value		11,180,398,000		14,419,474,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		0		0
AFS Securities		267,624,000		326,146,000
Derivative assets		0		0
Derivative liabilities		0
Total assets at fair value		267,624,000		326,146,000
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for portfolio		14,931,000		7,850,000
Real estate owned fair value disclosure		1,112,000		2,449,000
Total assets at fair value		16,043,000		10,299,000
Interest Rate Swap [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		153,534,000		124,050,000
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		(3,578,000)		(5,845,000)
Interest Rate Swap [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0		0
Derivative liabilities		0		0
Interest Rate Swap [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		7,403,000		16,172,000	[4]
Derivative liabilities		5,226,000		8,790,000
Interest Rate Swap [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0		0
Derivative liabilities		0		0
U.S. Treasury obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		1,028,642,000		3,390,772,000
U.S. Treasury obligations | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities				0
U.S. Treasury obligations | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		0		0
U.S. Treasury obligations | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		1,028,642,000		3,390,772,000
U.S. Treasury obligations | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		0		0
GSE and TVA obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		258,906,000		240,878,000
AFS Securities		1,658,671,000		1,550,699,000
GSE and TVA obligations | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		0		0
AFS Securities		0		0
GSE and TVA obligations | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		258,906,000		240,878,000
AFS Securities		1,658,671,000		1,550,699,000
GSE and TVA obligations | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		0		0
AFS Securities		0		0
State or local agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		247,890,000		247,894,000
State or local agency obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		0		0
State or local agency obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		247,890,000		247,894,000
State or local agency obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		0		0
U.S. obligations single-family MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		658,687,000		807,586,000
U.S. obligations single-family MBS | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		0		0
U.S. obligations single-family MBS | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		658,687,000		807,586,000
U.S. obligations single-family MBS | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		0		0
Private label MBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		267,624,000		326,146,000
Private label MBS [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		0		0
Private label MBS [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		0		0
Private label MBS [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		267,624,000		326,146,000
Mortgage Receivable [Member] | Forward Contracts [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset		0		0
Mortgage Receivable [Member] | Forward Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0		0
Derivative liabilities		0
Mortgage Receivable [Member] | Forward Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		49,000		29,000
Derivative liabilities		103,000		79,000
Mortgage Receivable [Member] | Forward Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0		0
Derivative liabilities		0
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		1,287,548,000		3,631,650,000
AFS Securities		10,153,022,000		11,097,769,000
Derivative assets		160,986,000		140,251,000
Derivative liabilities		1,751,000		3,024,000
Estimate of Fair Value Measurement [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		1,287,548,000		3,631,650,000
AFS Securities		10,153,022,000		11,097,769,000
Derivative assets		160,986,000		140,251,000
Derivative liabilities	[4]	1,751,000		3,024,000
Total assets at fair value		11,601,556,000		14,869,670,000
Estimate of Fair Value Measurement [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for portfolio		14,931,000		7,850,000
Real estate owned fair value disclosure		1,112,000		2,449,000
Total assets at fair value		16,043,000		10,299,000
Estimate of Fair Value Measurement [Member] | Interest Rate Swap [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		160,937,000		140,222,000
Derivative liabilities		1,648,000		2,945,000
Estimate of Fair Value Measurement [Member] | U.S. Treasury obligations | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		1,028,642,000		3,390,772,000
Estimate of Fair Value Measurement [Member] | GSE and TVA obligations | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities		258,906,000		240,878,000
AFS Securities		1,658,671,000		1,550,699,000
Estimate of Fair Value Measurement [Member] | State or local agency obligations [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		247,890,000		247,894,000
Estimate of Fair Value Measurement [Member] | U.S. obligations single-family MBS | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		658,687,000		807,586,000
Estimate of Fair Value Measurement [Member] | Mortgage Receivable [Member] | Forward Contracts [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		49,000		29,000
Derivative liabilities		103,000		79,000
Single Family [Member] | GSE MBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		3,704,537,000		4,055,859,000
Single Family [Member] | GSE MBS [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		0		0
Single Family [Member] | GSE MBS [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		3,704,537,000		4,055,859,000
Single Family [Member] | GSE MBS [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		0		0
Single Family [Member] | Estimate of Fair Value Measurement [Member] | GSE MBS [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		3,704,537,000		4,055,859,000
Multifamily [Member] | GSE MBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		3,615,613,000		4,109,585,000
Multifamily [Member] | GSE MBS [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		0		0
Multifamily [Member] | GSE MBS [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		3,615,613,000		4,109,585,000
Multifamily [Member] | GSE MBS [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		0		0
Multifamily [Member] | Estimate of Fair Value Measurement [Member] | GSE MBS [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		3,615,613,000		4,109,585,000
Residential Mortgage Backed Securities [Member] | Estimate of Fair Value Measurement [Member] | Private label MBS [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
AFS Securities		$ 267,624,000		$ 326,146,000

[1] Amounts represent the application of the netting requirements that allow the Bank to settle positive and negative positions, cash collateral and related accrued interest held or placed with the same clearing agent and/or counterparties. Cash collateral posted and related accrued interest was $160.0 million and $138.1 million at September 30, 2020 and December 31, 2019, respectively. Cash collateral received was $2.9 million for September 30, 2020 and $8.2 million for December 31, 2019.

[2] Amounts represent the application of the netting requirements that allow the Bank to settle positive and negative positions and also cash collateral held and related interest accrued or placed by the Bank with the same clearing agent and/or counterparties.

[3] ) Amounts represent the application of the netting requirements that allow the Bank to settle positive and negative positions and also cash collateral and related accrued interest held or placed by the Bank with the same clearing agent and/or counterparties.

[4] Derivative liabilities represent the total liabilities at fair value.