Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
OPERATING ACTIVITIES
Net income	$ 67,420	$ 77,236
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	12,323	11,843
Provision for credit loss expense	1,445	23,134
Gain on sale of investments	(5,471)	(32,095)
Net accretion of investment securities and assets	(12,018)	(14,975)
Net amortization on borrowings	134	136
Stock-based compensation expense	3,852	4,506
Gain on sale of premises held for sale	(177)	0
Gain on sale of foreclosed assets held for sale	(134)	(520)
Gain on sale of mortgage loans held for sale	(11,409)	(5,843)
Gain on sale of other intangibles	0	(301)
Gain on sale of banking operations	(5,300)	(5,889)
Deferred income taxes	3,227	(1,586)
Income from bank owned life insurance	(1,534)	(1,800)
Originations of mortgage loans held for sale	(298,914)	(182,550)
Proceeds from sale of mortgage loans held for sale	384,046	196,511
Changes in assets and liabilities:
Interest receivable	1,237	5,058
Other assets	(30,187)	1,325
Accrued interest and other liabilities	(20,733)	50,643
Income taxes payable	(12,055)	(21,221)
Net cash provided by operating activities	75,752	103,612
INVESTING ACTIVITIES
Net change in loans	705,540	(49,104)
Proceeds from sale of loans	1,847	0
Decrease in due from banks - time	245	245
Purchases of premises and equipment, net	(2,514)	(10,570)
Proceeds from sale of premises held for sale	1,572	0
Proceeds from sale of foreclosed assets held for sale	8,338	2,464
Proceeds from sale of available-for-sale securities	135,651	1,076,858
Proceeds from maturities of available-for-sale securities	185,636	1,255,991
Purchases of available-for-sale securities	(1,464,377)	(1,458,730)
Proceeds from maturities of held-to-maturity securities	4,426	3,561
Purchases of held-to-maturity securities	(280,043)	(16,997)
Proceeds from bank owned life insurance death benefits	573	763
Disposition of assets and liabilities held for sale	(134,166)	123,610
Net cash (used in) provided by investing activities	(837,272)	928,091
FINANCING ACTIVITIES
Net change in deposits	1,192,740	(503,567)
Dividends paid on preferred stock	(13)	(13)
Dividends paid on common stock	(19,500)	(19,077)
Net change in other borrowed funds	(1,600)	99,230
Net change in federal funds purchased and securities sold under agreements to repurchase	23,942	227,714
Net shares issued (cancelled) under stock compensation plans	1,172	(3,063)
Shares issued under employee stock purchase plan	1,170	956
Repurchases of common stock	(3,080)	(93,307)
Net cash provided by (used in) financing activities	1,194,831	(291,127)
INCREASE IN CASH AND CASH EQUIVALENTS	433,311	740,576
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	3,472,152	996,623
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 3,905,463	$ 1,737,199