FHLB Advances, Other Borrowings and Subordinated Notes (Summary of Debt) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Sep. 18, 2018
Debt Disclosure [Abstract]
FHLB advances	$ 1,228,416	$ 674,870	$ 574,823
Other borrowings:
Notes payable	112,401	123,090	133,776	$ 150,000
Short-term borrowings	8,458	20,520	10,182
Other	65,980	46,447	47,072
Secured borrowings	321,696	228,117	227,027
Total other borrowings	508,535	418,174	418,057
Subordinated notes	436,298	436,095	436,021
Total FHLB advances, other borrowings and subordinated notes	$ 2,173,249	$ 1,529,139	$ 1,428,901