CONSOLIDATED STATEMENTS OF CASH FLOWS - 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:
Depreciation and amortization	57,615	53,317	27,554
Stock-based compensation	16,154	14,726	19,472
Provision for credit losses	125,722	24,218	32,501
Net amortization of premiums and accretion of discounts on securities and borrowings	38,315	29,512	38,454
Amortization of other intangible assets	24,645	18,080	18,416
(Gains) losses on securities transactions, net	(524)	150	2,342
Proceeds from sales of loans held for sale	1,019,841	509,448	398,350
Gains on sales of loans, net	(42,251)	(18,914)	(20,515)
Net impairment losses on securities recognized in earnings	0	2,928	0
Originations of loans held for sale	(1,211,227)	(537,985)	(406,087)
Losses (gains) on sales of assets, net	1,891	(78,333)	2,401
Net deferred income tax (benefit) expense	(5,060)	15,228	(11,780)
Net change in:
Cash surrender value of bank owned life insurance	(10,083)	(8,232)	(8,691)
Accrued interest receivable	(593)	1,440	(9,183)
Other assets	(311,760)	(163,330)	(33,144)
Accrued expenses and other liabilities	58,234	57,882	(7,562)
Net cash provided by operating activities	151,525	229,928	303,956
Cash flows from investing activities:
Net loan originations and purchases	(2,490,937)	(2,538,909)	(3,257,939)
Equity securities:
Purchases	(8,337)	(14,776)	0
Sales	28,439	24,748	0
Held to maturity debt securities:
Purchases	(682,509)	(701,879)	(264,721)
Maturities, calls and principal repayments	824,477	424,475	241,077
Available for sale debt securities:
Purchases	(333,971)	(30,392)	(289,554)
Sales	30,020	271,901	44,377
Maturities, calls and principal repayments	555,589	316,024	255,031
Death benefit proceeds from bank owned life insurance	15,043	9,560	4,220
Proceeds from sales of real estate property and equipment	19,111	109,043	7,786
Proceeds from sales of loans held for investments	30,020	1,234,022	289,633
Purchases of real estate property and equipment	(24,607)	(23,375)	(26,440)
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:
Net change in deposits	2,749,765	1,808,148	2,734,669
Net change in short-term borrowings	54,678	(1,036,134)	720,307
Proceeds from issuance of long-term borrowings, net	838,388	950,000	0
Repayments of long-term borrowings	(667,739)	(890,000)	(750,682)
Cash dividends paid to preferred shareholders	(12,688)	(12,688)	(15,859)
Cash 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
Other, net	(612)	(492)	0
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
Supplemental disclosures of cash flow information:
Interest on deposits and borrowings	279,042	415,649	290,444
Federal and state income taxes	148,383	106,336	53,587
Supplemental schedule of non-cash investing activities:
Transfer of loans to other real estate owned	4,040	5,100	743
Loans transferred to loans held for sale	30,020	1,234,022	289,633
Lease right of use assets obtained in exchange for operating lease liabilities	16,062	312,143	0
Non-cash assets acquired:
Equity securities	0	51,382	0
Loans	0	3,378,358	3,736,984
Premises and equipment	0	23,585	62,066
Bank owned life insurance	0	101,896	49,052
Accrued interest receivable	0	11,781	12,123
Goodwill	0	297,777	394,028
Other intangible assets	0	20,690	45,906
Other assets	0	50,873	100,059
Total non-cash assets acquired	0	4,277,113	4,922,820
Liabilities assumed:
Deposits	0	2,924,716	3,564,843
Short-term borrowings	0	10,500	649,979
Long-term borrowings	0	430,130	87,283
Junior subordinated debentures issued to capital trusts	0	0	13,249
Accrued expenses and other liabilities	0	98,751	26,848
Total liabilities assumed	0	3,464,097	4,342,202
Net non-cash assets acquired	0	813,016	580,618
Net cash and cash equivalents acquired in acquisition	0	22,239	156,612
Common stock issued in acquisition	0	835,255	737,230
Available-for-sale securities
Non-cash assets acquired:
Investment securities	0	335,894	308,385
Held-to-maturity securities
Non-cash assets acquired:
Investment securities	$ 0	$ 4,877	$ 214,217