Parent Company Information - Schedule of Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net Income	$ 390,606	$ 309,793	$ 261,428
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation	16,154	14,726	19,472
Net amortization of premiums and accretion of discounts on borrowings	38,315	29,512	38,454
(Gains) losses on securities transactions, net	(524)	150	2,342
Net change in:
Other assets	(311,760)	(163,330)	(33,144)
Net cash provided by operating activities	151,525	229,928	303,956
Cash flows from investing activities:
Purchases of equity securities	(8,337)	(14,776)	0
Sales of investment securities available for sale	30,020	271,901	44,377
Cash and cash equivalents acquired in acquisitions	0	22,239	156,612
Net cash used in investing activities	(2,037,662)	(897,319)	(2,839,918)
Cash flows from financing activities:
Proceeds from issuance of long-term borrowings, net	838,388	950,000	0
Dividends paid to preferred shareholders	(12,688)	(12,688)	(15,859)
Dividends paid to common shareholders	(177,965)	(146,537)	(138,857)
Purchase of common shares to treasury	(5,374)	(1,805)	(3,801)
Common stock issued, net	2,202	2,957	2,704
Net cash provided by financing activities	2,780,655	673,449	2,548,481
Net change in cash and cash equivalents	894,518	6,058	12,519
Cash and cash equivalents at beginning of year	434,687	428,629	416,110
Cash and cash equivalents at end of year	1,329,205	434,687	428,629
Parent Company
Cash flows from operating activities:
Net Income	390,606	309,793	261,428
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiary	(219,687)	(197,714)	(113,705)
Stock-based compensation	16,154	14,726	19,472
Net amortization of premiums and accretion of discounts on borrowings	230	124	63
(Gains) losses on securities transactions, net	0	0	(3)
Losses on sales of assets, net	0	0	147
Net change in:
Other assets	121	19,768	9,928
Accrued expenses and other liabilities	17,905	8,803	(10,657)
Net cash provided by operating activities	205,329	155,500	166,673
Cash flows from investing activities:
Purchases of equity securities	(2,500)	0	0
Sales of investment securities available for sale	0	0	257
Cash and cash equivalents acquired in acquisitions	0	11,947	7,915
Repayment of subordinated debt by subsidiary	100,000	0	0
Capital contributions to subsidiary	(210,000)	0	0
Other, net	(1,200)	0	0
Net cash used in investing activities	(113,700)	11,947	8,172
Cash flows from financing activities:
Proceeds from issuance of long-term borrowings, net	113,146	0	0
Dividends paid to preferred shareholders	(12,688)	(12,688)	(15,859)
Dividends paid to common shareholders	(177,965)	(146,537)	(138,857)
Purchase of common shares to treasury	(5,374)	(1,805)	(3,801)
Common stock issued, net	2,202	2,957	2,704
Net cash provided by financing activities	(80,679)	(158,073)	(155,813)
Net change in cash and cash equivalents	10,950	9,374	19,032
Cash and cash equivalents at beginning of year	119,213	109,839	90,807
Cash and cash equivalents at end of year	$ 130,163	$ 119,213	$ 109,839