Trading Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Schedule of Trading Securities [Line Items]
Trading securities	$ 1,675,212	$ 1,956,923
Trading Securities, Net Unrealized Gain (Loss)	3,941	10,969
U.S. government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading securities	63,334	63,765
Trading Securities, Net Unrealized Gain (Loss)	23	254
Residential agency mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	1,480,458	1,791,584
Trading Securities, Net Unrealized Gain (Loss)	3,851	9,966
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	44,105	34,507
Trading Securities, Net Unrealized Gain (Loss)	(99)	(1)
Asset-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	36,928	42,656
Trading Securities, Net Unrealized Gain (Loss)	50	685
Other debt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	50,387	24,411
Trading Securities, Net Unrealized Gain (Loss)	$ 116	$ 65