FHLB Advances, Other Borrowings and Subordinated Notes (Summary of Debt) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Debt Disclosure [Abstract]
FHLB advances	$ 1,241,071	$ 1,228,429	$ 1,228,422
Other borrowings:
Notes payable	85,668	101,710	107,056
Short-term borrowings	14,051	11,366	7,983
Other	63,770	65,108	65,548
Secured borrowings	341,038	340,744	326,808
Total other borrowings	504,527	518,928	507,395
Subordinated notes	436,811	436,506	436,385
Total FHLB advances, other borrowings and subordinated notes	$ 2,182,409	$ 2,183,863	$ 2,172,202