Condensed Financial Information (Parent Company Only) - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
ASSETS
Cash and cash equivalents	$ 1,650,653	$ 3,472,152
Loans	12,012,503	12,900,897
Other assets	325,793	289,332
Total assets	24,724,759	22,359,752
LIABILITIES
Long-term debt	1,722,104
Total liabilities	21,475,918	19,383,096
Stockholders’ equity:
Preferred stock	0	767
Common stock	1,127	1,081
Surplus	2,164,989	2,014,076
Accumulated other comprehensive gain (loss):	1,093,270	901,006
Total stockholders’ equity	3,248,841	2,976,656	$ 2,988,924	$ 2,246,434
Total liabilities and stockholders’ equity	24,724,759	22,359,752
Parent Company
ASSETS
Cash and cash equivalents	175,711	172,083
Investment securities	2,932	1,648
Investments in wholly-owned subsidiaries	3,444,624	3,165,791
Loans	2,610	471
Intangible assets, net	133	133
Premises and equipment	23,861	25,606
Other assets	53,877	56,257
Total assets	3,703,748	3,421,989
LIABILITIES
Long-term debt	406,552	406,859
Other liabilities	48,355	38,474
Total liabilities	454,907	445,333
Stockholders’ equity:
Preferred stock	0	767
Common stock	1,127	1,081
Surplus	2,164,989	2,014,076
Accumulated other comprehensive gain (loss):	1,093,270	901,006
Unrealized appreciation on available-for-sale securities, net of income taxes of $(3,731) and $21,132 at December 31, 2020 and 2019 respectively	(10,545)	59,726
Total stockholders’ equity	3,248,841	2,976,656
Total liabilities and stockholders’ equity	$ 3,703,748	$ 3,421,989