Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities
Net income	$ 384,155	$ 370,249	$ 142,413
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization, and accretion, including amortization of purchase accounting adjustments and market value adjustments	16,360	(7,534)	(4,113)
Provision for credit losses	41,657	40,385	51,708
Share-based compensation expense - equity awards	24,584	20,278	16,436
(Gain) loss on sale of OREO and long-lived assets, net of impairment	(1,740)	4,429	1,581
Loss on sale of securities available-for-sale	979	49,900	148
Gain on early termination of FDIC loss share agreements	0	(2,708)	0
Cash paid for early termination of FDIC loss share agreements	0	(5,637)	0
Deferred income tax expense	30,703	153,518	71,257
Originations of mortgage loans held for sale	(1,967,532)	(1,469,847)	(1,844,358)
Proceeds from sales of mortgage loans held for sale	1,933,973	1,543,724	1,922,003
Realized and unrealized gain on mortgage loans held for sale, net	(64,825)	(45,338)	(62,438)
Other operating activities, net	180,506	(204,998)	(30,991)
Net Cash Provided by Operating Activities	578,820	446,421	263,646
Cash Flows from Investing Activities
Proceeds from sales of securities available-for-sale	299,513	1,035,482	682,349
Proceeds from maturities, prepayments and calls of securities available-for-sale	845,726	635,183	568,250
Purchases of securities available-for-sale, net of securities available-for-sale acquired	(210,237)	(1,959,952)	(1,475,008)
Proceeds from maturities, prepayments and calls of securities held to maturity	21,727	16,841	8,687
Purchases of held to maturity securities	0	0	(148,234)
Purchases of equity securities, net of equity securities acquired	(15,154)	(30,904)	(71,684)
Proceeds from sales of equity securities	43,284	88,200	21,532
Increase in loans, net of loans acquired	(1,477,677)	(949,953)	(976,488)
Proceeds from sales of premises and equipment	11,806	6,374	354
Purchases of premises and equipment, net of premises and equipment acquired	(35,000)	(13,730)	(37,763)
Proceeds from dispositions of OREO	13,136	15,810	25,624
Cash paid for additional investment in tax credit entities	(11,414)	(18,818)	(16,401)
Cash received (paid) for acquisition of a business, net of cash paid	0	99,318	(490,435)
Purchase of bank owned life insurance policies	0	(50,000)	0
Other investing activities, net	1,000	343	636
Net Cash Used in Investing Activities	(513,290)	(1,125,806)	(1,908,581)
Cash Flows from Financing Activities
Increase (decrease) in deposits, net of deposits acquired	1,455,918	1,232,603	(323,257)
Net change in short-term borrowings, net of borrowings acquired	(1,278,674)	491,585	(38,377)
Proceeds from long-term debt, net of long-term debt acquired	500,000	937,917	964,974
Repayments of long-term debt	(321,987)	(1,672,033)	(97,259)
Cash dividends paid on common stock	(92,190)	(84,782)	(72,772)
Cash dividends paid on preferred stock	(12,602)	(9,095)	(9,095)
Shares Issued, Value, Share-based Payment Arrangement, before Forfeiture	(3,373)	(3,226)	(832)
Payments to repurchase common stock	(204,740)	(148,855)	0
Net proceeds from issuance of common stock	0	0	485,151
Net proceeds from issuance of preferred stock	96,388	0	0
Net Cash Provided by Financing Activities	138,740	744,114	908,533
Net Increase (Decrease) In Cash and Cash Equivalents	204,270	64,729	(736,402)
Cash and Cash Equivalents at Beginning of Period	690,453	625,724	1,362,126
Cash and Cash Equivalents at End of Period	894,723	690,453	625,724
Supplemental Schedule of Non-cash Activities
Acquisition of real estate in settlement of loans	10,847	12,557	18,170
Common stock issued in acquisitions	0	214,659	211,043
Cash paid (received) for:
Interest on deposits and borrowings, net of acquired	319,675	198,905	102,558
Income taxes, net	$ (107,401)	$ 34,313	$ 77,034