FHLB Advances, Other Borrowings and Subordinated Notes (Summary of Debt) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Sep. 18, 2018
Debt Disclosure [Abstract]
FHLB advances	$ 1,174,894	$ 674,870	$ 576,353
Other borrowings:
Notes payable	167,746	123,090	139,119	$ 150,000
Short-term borrowings	12,127	20,520	16,212
Other	66,266	46,447	47,394
Secured borrowings	241,364	228,117	169,469
Total other borrowings	487,503	418,174	372,194
Subordinated notes	436,179	436,095	139,235
Total FHLB advances, other borrowings and subordinated notes	$ 2,098,576	$ 1,529,139	$ 1,087,782