Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
OPERATING ACTIVITIES
Net income	$ 222,918	$ 201,936
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	35,396	36,590
Provision for credit losses	(31,396)	68,030
Gain on sale of investments	(15,846)	(54,790)
Net accretion of investment securities and assets	(36,929)	(43,286)
Net amortization on borrowings	404	406
Stock-based compensation expense	12,591	10,750
Gain on sale of premises held for sale	(591)	(33)
Gain on sale of foreclosed assets held for sale	(76)	(475)
Gain on sale of mortgage loans held for sale	(29,222)	(28,994)
Gain on sale of other intangibles	0	(301)
Gain on sale of banking operations	(5,316)	(8,094)
Fair value write-down of closed branches	0	1,465
Deferred income taxes	3,585	2,920
Income from bank owned life insurance	(6,229)	(4,983)
Originations of mortgage loans held for sale	(752,480)	(851,356)
Proceeds from sale of mortgage loans held for sale	884,452	745,723
Changes in assets and liabilities:
Interest receivable	4,191	(15,601)
Other assets	(22,677)	(7,009)
Accrued interest and other liabilities	(41,674)	43,696
Income taxes payable	(1,199)	(20,206)
Net cash provided by operating activities	219,902	76,388
INVESTING ACTIVITIES
Net change in loans	2,056,058	243,826
Proceeds from sale of loans	26,472	32,742
Net change in due from banks - time	(201)	493
Purchases of premises and equipment, net	(36,832)	(22,697)
Proceeds from sale of premises held for sale	5,621	123
Proceeds from sale of foreclosed assets held for sale	14,594	9,705
Proceeds from sale of available-for-sale securities	342,577	1,717,364
Proceeds from maturities of available-for-sale securities	559,259	2,218,259
Purchases of available-for-sale securities	(4,786,533)	(3,169,534)
Proceeds from maturities of held-to-maturity securities	13,804	10,520
Purchases of held-to-maturity securities	(694,734)	(16,997)
Purchases of bank owned life insurance	(160,000)	0
Proceeds from bank owned life insurance death benefits	3,814	1,425
Disposition of assets and liabilities held for sale	(134,166)	181,271
Net cash (used in) provided by investing activities	(2,790,267)	1,206,500
FINANCING ACTIVITIES
Net change in deposits	1,075,422	191,714
Repayments of subordinated debentures	0	(5,927)
Dividends paid on preferred stock	(39)	(39)
Dividends paid on common stock	(58,319)	(56,141)
Net change in other borrowed funds	(3,482)	45,170
Net change in federal funds purchased and securities sold under agreements to repurchase	(81,835)	163,549
Net shares issued (cancelled) under stock compensation plans	1,222	(3,355)
Shares issued under employee stock purchase plan	1,170	956
Repurchases of common stock	(54,513)	(93,307)
Net cash provided by financing activities	879,626	242,620
(DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(1,690,739)	1,525,508
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	3,472,152	996,623
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 1,781,413	$ 2,522,131