Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
OPERATING ACTIVITIES
Net income	$ 238,167	$ 215,713	$ 92,940
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	36,257	28,412	21,062
Provision for loan losses	43,240	38,148	26,393
Gain on sale of investments	(13,314)	(61)	(1,059)
Net accretion of investment securities and assets	(53,619)	(48,684)	(38,090)
Net amortization (accretion) on borrowings	394	(380)	561
Stock-based compensation expense	12,921	9,725	10,681
Gain on sale of premises and equipment held for sale, net of impairment	0	0	(615)
Gain on sale of foreclosed assets and other real estate owned	(33)	(650)	(1,076)
Gain on sale of mortgage loans held for sale	(20,064)	(12,844)	(12,186)
Loss (gain) on sale of loans	4,451	(10)	(18)
Gain on sale of Visa, Inc. class B common stock	(42,860)
Fair value write-down of closed branches	0	836	325
Deferred income taxes	34,911	8,412	23,251
Gain on sale of insurance lines of business	0	0	(3,708)
Income from bank owned life insurance	(4,854)	(5,003)	(3,503)
Originations of mortgage loans held for sale	(755,500)	(546,676)	(507,907)
Proceeds from sale of mortgage loans held for sale	756,642	556,759	526,245
Changes in assets and liabilities:
Interest receivable	3,231	(6,227)	(2,432)
Assets held in trading accounts	0	0	41
Other assets	42,189	(1,414)	12,456
Accrued interest and other liabilities	(35,886)	33,978	(14,194)
Income taxes payable	20,074	(9,355)	(14,604)
Net cash provided by operating activities	266,347	260,679	114,563
INVESTING ACTIVITIES
Net collections (originations) of loans	23,806	(912,793)	(719,219)
Proceeds from sale of loans	104,587	24,977	20,705
Decrease (increase) in due from banks - time	1,130	(1,620)	3,233
Purchases of premises and equipment, net	(67,831)	(29,740)	(34,216)
Proceeds from sale of premises and equipment	0	0	3,475
Purchases of other real estate owned	0	0	(1,021)
Proceeds from sale of foreclosed assets and other real estate owned	17,986	27,751	18,255
Proceeds from sale of available-for-sale securities	1,235,030	7,959	679,613
Proceeds from maturities of available-for-sale securities	776,084	258,325	487,717
Purchases of available-for-sale securities	(1,710,483)	(825,914)	(854,708)
Proceeds from maturities of held-to-maturity securities	31,969	80,803	97,494
Purchases of held-to-maturity securities	0	(1,172)	(860)
Proceeds from bank owned life insurance death benefits	2,435	1,814	0
Purchases of bank owned life insurance	0	(4,000)	(143)
Proceeds from the sale of insurance lines of business	0	0	9,296
Cash received (paid) in business combinations	178,260	0	(48,092)
Disposition of assets and liabilities held for sale	1,235	(55,211)	0
Net cash provided by (used in) investing activities	594,208	(1,428,821)	(338,471)
FINANCING ACTIVITIES
Net change in deposits	(404,826)	1,305,877	120,667
Proceeds from issuance of subordinated notes and other borrowings	25,500	326,355	0
Repayments of subordinated debentures and subordinated debt	0	(113,990)	(3,000)
Dividends paid on preferred stock	(339)	0	0
Dividends paid on common stock	(63,921)	(55,646)	(35,116)
Net change in other borrowed funds	(240,806)	(34,574)	521,865
Net change in federal funds purchased and securities sold under agreements to repurchase	40,207	(26,652)	(71,003)
Net shares (cancelled) issued under stock compensation plans	(2,389)	1,162	2,260
Shares issued under employee stock purchase plan	1,312	1,026	618
Repurchase of common stock	(10,128)	0	0
Retirement of preferred stock	(42,000)	0	0
Net cash (used in) provided by financing activities	(697,390)	1,403,558	536,291
INCREASE IN CASH EQUIVALENTS	163,165	235,416	312,383
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	833,458	598,042	285,659
CASH AND CASH EQUIVALENTS, END OF YEAR	$ 996,623	$ 833,458	$ 598,042