Securities - Trading Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule of fair value of trading securities
Debt Securities, Trading	$ 393,581	$ 689,576
Investment-related Liabilities
Securities sold, not yet purchased, at fair value	22,768	43,817
US Treasury Securities
Schedule of fair value of trading securities
Debt Securities, Trading	1,485
Bonds
Schedule of fair value of trading securities
Debt Securities, Trading		24,680
Residential Mortgage Backed Securities
Schedule of fair value of trading securities
Debt Securities, Trading	164,899	331,601
Commercial mortgage-backed securities
Schedule of fair value of trading securities
Debt Securities, Trading	2,136	2,145
Collateralized Mortgage Obligations
Schedule of fair value of trading securities
Debt Securities, Trading	80,262	191,154
Corporate debt securities
Schedule of fair value of trading securities
Debt Securities, Trading	28,893	36,973
States and political subdivisions
Schedule of fair value of trading securities
Debt Securities, Trading	103,075	93,117
Unit investment trusts
Schedule of fair value of trading securities
Debt Securities, Trading		3,468
Private-label securitized product
Schedule of fair value of trading securities
Debt Securities, Trading	650	2,992
Other
Schedule of fair value of trading securities
Debt Securities, Trading	$ 12,181	$ 3,446