Trading Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Trading Securities [Line Items]
Trading securities	$ 2,245,480	$ 1,623,921
Trading Securities, Net Unrealized Gain (Loss)	(677)	2,359
U.S. government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading securities	5,181	44,264
Trading Securities, Net Unrealized Gain (Loss)	(1)	6
Residential agency mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	2,150,759	1,504,651
Trading Securities, Net Unrealized Gain (Loss)	(693)	2,293
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	30,533	26,196
Trading Securities, Net Unrealized Gain (Loss)	(44)	60
Asset-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	0	14,084
Trading Securities, Net Unrealized Gain (Loss)	0	(21)
Other debt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	59,007	34,726
Trading Securities, Net Unrealized Gain (Loss)	$ 61	$ 21