Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
OPERATING ACTIVITIES
Net income	$ 77,236	$ 47,695
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	11,843	7,451
Provision for credit loss expense	26,134	9,285
(Benefit) provision for credit losses on unfunded commitments	(3,000)	300
Gain on sale of investments	(32,095)	(2,740)
Net accretion of investment securities and assets	(14,975)	(9,559)
Net amortization on borrowings	136	91
Stock-based compensation expense	4,506	3,084
Gain on sale of foreclosed assets held for sale	(520)	(32)
Gain on sale of mortgage loans held for sale	(5,843)	(3,342)
Gain on sale of other intangibles	(301)	0
Gain on sale of branches	(5,889)	0
Deferred income taxes	(1,586)	2,081
Income from bank owned life insurance	(1,800)	(876)
Originations of mortgage loans held for sale	(182,550)	(98,255)
Proceeds from sale of mortgage loans held for sale	196,511	109,916
Changes in assets and liabilities:
Interest receivable	5,058	(1,858)
Lease right-of-use assets	2,330	2,294
Other assets	1,325	10,982
Accrued interest and other liabilities	48,313	30,505
Income taxes payable	(21,221)	(10,977)
Net cash provided by operating activities	103,612	96,045
INVESTING ACTIVITIES
Net originations of loans	(49,104)	(18,116)
Decrease in due from banks - time	245	250
Purchases of premises and equipment, net	(10,570)	(13,027)
Proceeds from sale of foreclosed assets held for sale	2,464	7,214
Proceeds from sale of available-for-sale securities	1,076,858	201,516
Proceeds from maturities of available-for-sale securities	1,255,991	56,438
Purchases of available-for-sale securities	(1,458,730)	(110,201)
Proceeds from maturities of held-to-maturity securities	3,561	11,408
Purchases of held-to-maturity securities	(16,997)	0
Proceeds from bank owned life insurance death benefits	763	1,310
Disposition of assets and liabilities held for sale	123,610	1,393
Net cash provided by investing activities	928,091	138,185
FINANCING ACTIVITIES
Net change in deposits	(503,567)	(409,221)
Dividends paid on preferred stock	(13)	0
Dividends paid on common stock	(19,077)	(14,807)
Net change in other borrowed funds	99,230	(175,461)
Net change in federal funds purchased and securities sold under agreements to repurchase	227,714	24,421
Net shares cancelled under stock compensation plans	(3,063)	(2,771)
Shares issued under employee stock purchase plan	956	1,312
Repurchases of common stock	(93,307)	0
Net cash used in financing activities	(291,127)	(576,527)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	740,576	(342,297)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	996,623	833,458
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 1,737,199	$ 491,161