Trading Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule of Trading Securities [Line Items]
Trading securities	$ 2,110,585	$ 1,623,921
Trading Securities, Net Unrealized Gain (Loss)	22,846	2,359
U.S. government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading securities	37,740	44,264
Trading Securities, Net Unrealized Gain (Loss)	264	6
Residential agency mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	1,922,725	1,504,651
Trading Securities, Net Unrealized Gain (Loss)	26,195	2,293
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	35,513	26,196
Trading Securities, Net Unrealized Gain (Loss)	(289)	60
Asset-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	58,278	14,084
Trading Securities, Net Unrealized Gain (Loss)	(2,381)	(21)
Other debt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	56,329	34,726
Trading Securities, Net Unrealized Gain (Loss)	$ (943)	$ 21