FHLB Advances, Other Borrowings and Subordinated Notes (Summary of Debt) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Debt Disclosure [Abstract]
FHLB advances	$ 667,000	$ 559,663	$ 318,270
Other borrowings:
Notes payable	29,982	41,222	44,959
Short-term borrowings	21,437	17,209	46,280
Other	48,369	49,131	49,765
Secured borrowings	155,913	158,561	136,706
Total other borrowings	255,701	266,123	277,710
Subordinated notes	139,148	139,088	139,029
Total FHLB advances, other borrowings and subordinated notes	$ 1,061,849	$ 964,874	$ 735,009