Trading Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Trading Securities [Line Items]
Trading securities	$ 1,196,105	$ 1,623,921
Trading Securities, Net Unrealized Gain (Loss)	3,851	2,359
U.S. government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading securities	4,237	44,264
Trading Securities, Net Unrealized Gain (Loss)	19	6
Residential agency mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	1,146,454	1,504,651
Trading Securities, Net Unrealized Gain (Loss)	3,589	2,293
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	22,710	26,196
Trading Securities, Net Unrealized Gain (Loss)	116	60
Asset-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	5	14,084
Trading Securities, Net Unrealized Gain (Loss)	0	(21)
Other debt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	22,699	34,726
Trading Securities, Net Unrealized Gain (Loss)	$ 127	$ 21