Consolidated Statements of Cash Flow $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income (Loss) Attributable to Parent	$ (1,523,420)	$ 354,095	$ 316,263
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Deferred income tax (benefit) expense	(62,943)	(3,544)	18,812
Amortization of investment premiums, net	27,069	26,449	9,917
(Gain) loss on sales of investment securities, net	(190)	7,184	(14)
Provision for credit losses	204,861	72,515	55,905
Change in cash surrender value of bank owned life insurance	(8,500)	(8,443)	(8,396)
Depreciation, amortization and accretion	37,474	43,286	52,345
Gain on sale of premises and equipment	(2,284)	(2,821)	(2,037)
Gain on store divestiture	(9,650)	(1,225)	(1,157)
Gain on Pivotus divestiture	0	0	(5,778)
Goodwill impairment	1,784,936	0	0
Additions to residential mortgage servicing rights carried at fair value	(51,000)	(25,169)	(29,069)
Change in fair value residential mortgage servicing rights carried at fair value	73,103	44,783	13,195
Gain on redemption of junior subordinated debentures at amortized cost	0	0	(1,043)
Stock-based compensation	9,254	8,373	7,513
Net (increase) decrease in equity and other investments	(2,143)	(16,702)	900
(Gain) loss on equity securities, net	(769)	(83,475)	1,484
Gain on sale of loans and leases, net	(289,212)	(95,353)	(77,772)
Change in fair value of loans held for sale	(16,776)	(10,557)	2,606
Origination of loans held for sale	(6,666,500)	(3,089,698)	(2,872,994)
Proceeds from sales of loans held for sale	6,791,133	2,838,171	3,033,383
Change in other assets and liabilities:
Net increase in other assets	(209,822)	(137,981)	(28,312)
Net increase (decrease) in other liabilities	9,153	(367)	19,493
Net cash provided by (used in) operating activities	93,774	(80,479)	505,244
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of investment securities available for sale	(867,675)	(697,969)	(449,359)
Proceeds from investment securities available for sale	828,752	918,658	440,241
Proceeds from sale of equity securities	0	81,853	0
Purchases of restricted equity securities	(20,021)	(220,200)	(45,601)
Redemption of restricted equity securities	24,818	214,005	48,841
Net change in loans and leases	(862,125)	(1,085,272)	(1,618,333)
Proceeds from sales of loans and leases	111,855	251,782	164,037
Change in premises and equipment	(11,986)	(12,676)	(8,989)
Proceeds from bank owned life insurance death benefits	5,641	1,869	1,481
Payments for (Proceeds from) Mortgage Servicing Rights	0	34,401	0
Net cash paid in store divestiture	(171,440)	(44,646)	(35,219)
Other	2,070	8,044	3,716
Net cash used in investing activities	(960,111)	(550,151)	(1,499,185)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in deposit liabilities	2,341,319	1,393,940	1,226,507
Net increase in securities sold under agreements to repurchase	64,076	14,157	2,852
Proceeds from borrowings	600,000	940,670	100,000
Repayment of borrowings	(735,000)	(785,670)	(150,652)
Repayment of junior subordinated debentures at amortized cost	0	0	(10,598)
Dividends paid on common stock	(184,978)	(185,101)	(173,914)
Proceeds from stock options exercised	0	21	1,065
Repurchase and retirement of common stock	(8,655)	(7,268)	(12,962)
Net cash provided by financing activities	2,076,762	1,370,749	982,298
Net increase (decrease) in cash and cash equivalents	1,210,425	740,119	(11,643)
Cash and cash equivalents, beginning of period	1,362,756	622,637	634,280
Cash and cash equivalents, end of period	2,573,181	1,362,756	622,637
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Interest	136,018	209,526	124,333
Income taxes	130,228	129,616	71,985
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Change in unrealized gains and losses on investment securities available for sale, net of taxes	79,200	69,238	(26,304)
Change in unrealized gains and losses on junior subordinated debentures carried at fair value, net of taxes	13,996	19,225	(17,328)
Cumulative effect adjustment to retained earnings	40,181	244	9,710
Cash dividend declared on common stock and payable after period-end	0	46,248	46,254
Transfer of loans to loans held for sale	78,146	0	0
Change in GNMA mortgage loans recognized due to repurchase option	$ (4,337)	$ (4,581)	$ (3,510)