Available-for-Sale Securities Major Security Types (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	$ 7,482,922	$ 6,002,902
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		8,432	869
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(82,354)	(153,827)
Available-for-sale securities Fair Value		7,409,000	5,849,944
States or local housing-finance-agency obligations (HFA securities) [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	69,320	55,500
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		0	0
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(4,668)	(5,899)
Available-for-sale securities Fair Value		64,652	49,601
Supranational institutions [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	429,354	419,222
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		0	0
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(12,925)	(14,067)
Available-for-sale securities Fair Value		416,429	405,155
U.S. government-owned corporations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	323,192	297,729
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		0	0
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(26,431)	(24,560)
Available-for-sale securities Fair Value		296,761	273,169
GSEs [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	130,935	122,423
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		0	0
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(7,149)	(6,796)
Available-for-sale securities Fair Value		123,786	115,627
Other Than Mortgage-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	952,801	894,874
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		0	0
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(51,173)	(51,322)
Available-for-sale securities Fair Value		901,628	843,552
U.S. government-guaranteed - single-family MBS [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	60,003	79,075
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		0	20
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(2,289)	(3,437)
Available-for-sale securities Fair Value		57,714	75,658
U.S. government guaranteed - multifamily MBS [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	283,674	368,103
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		0	0
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(1,057)	(6,969)
Available-for-sale securities Fair Value		282,617	361,134
MBS [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	6,530,121	5,108,028
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		8,432	869
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(31,181)	(102,505)
Available-for-sale securities Fair Value		6,507,372	5,006,392
Single Family [Member] | GSEs – MBS [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	2,598,325	3,649,964
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		5,323	681
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(13,377)	(88,486)
Available-for-sale securities Fair Value		2,590,271	3,562,159
Multifamily [Member] | GSEs – MBS [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	[1]	3,588,119	1,010,886
Unrealized Gains Amounts Recorded in Accumulated Other Comprehensive Loss		3,109	168
Unrealized Losses Amounts Recorded in Accumulated Other Comprehensive Loss		(14,458)	(3,613)
Available-for-sale securities Fair Value		$ 3,576,770	$ 1,007,441

[1] Amortized cost of available-for-sale securities includes adjustments made to the cost basis of an investment for accretion, amortization, collection of cash, and fair-value hedge accounting adjustments.