FHLB Advances, Other Borrowings and Subordinated Notes (Summary of Debt) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Sep. 18, 2018
Debt Disclosure [Abstract]
FHLB advances	$ 1,228,422	$ 674,870	$ 574,847
Other borrowings:
Notes payable	107,056	123,090	128,433	$ 150,000
Short-term borrowings	7,983	20,520	9,677
Other	65,548	46,447	46,774
Secured borrowings	326,808	228,117	225,604
Total other borrowings	507,395	418,174	410,488
Subordinated notes	436,385	436,095	435,979
Total FHLB advances, other borrowings and subordinated notes	$ 2,172,202	$ 1,529,139	$ 1,421,314