Condensed Financial Information - Parent Company Only Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
ASSETS
Other assets	$ 1,078,128	$ 855,470
Investments in:
Total Assets	25,906,733	21,886,040
Other liabilities	514,004	376,107
Total Liabilities	23,289,905	19,543,864
Shareholders' Equity [Abstract]
Shareholders’ equity	2,616,828	2,342,176	$ 2,247,573	$ 2,229,857
Total Liabilities and Shareholders’ Equity	25,906,733	21,886,040
Parent
ASSETS
Cash and cash equivalents	10,063	10,841	$ 30,941	$ 22,857
Other assets	28,940	1,087
Receivable from subsidiaries	53,438	78,025
Investments in:
Bank subsidiary	3,045,529	2,555,448
Non-bank subsidiaries	313,003	419,145
Total Assets	3,450,973	3,064,546
Long-term borrowings	759,782	387,756
Payable to non-bank subsidiaries	0	276,768
Other liabilities	74,363	57,846
Total Liabilities	834,145	722,370
Shareholders' Equity [Abstract]
Shareholders’ equity	2,616,828	2,342,176
Total Liabilities and Shareholders’ Equity	$ 3,450,973	$ 3,064,546