Securities Fair Value Option Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value Option Securities [Line Items]
Fair value option securities, Fair Value	$ 722,657	$ 1,098,577
Fair value option securities, Net Unrealized Gain (Loss)	16,856	14,061
U.S. Treasury [Member]
Fair Value Option Securities [Line Items]
Fair value option securities, Fair Value	92,742	9,917
Fair value option securities, Net Unrealized Gain (Loss)	307	(48)
Residential agency mortgage-backed securities [Member]
Fair Value Option Securities [Line Items]
Fair value option securities, Fair Value	629,915	1,088,660
Fair value option securities, Net Unrealized Gain (Loss)	$ 16,549	$ 14,109