Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities:
Net income	$ 292,990	$ 355,697	$ 343,166
Adjustments to reconcile net income to net cash provided by operating activities
Provision for credit losses	214,220	53,864	34,832
Depreciation, amortization and accretion, net	96,369	88,362	67,665
Deferred income tax (benefit) expense	(4,058)	44,557	55,224
Stock-based compensation (benefit) expense	(4,938)	11,304	13,496
Net amortization of premium on securities	10,881	6,605	7,411
Accretion of discounts on loans	(81,604)	(26,624)	(20,318)
Mortgage servicing rights fair value change, net	62,859	35,536	5,370
Originations and purchases of mortgage loans held-for-sale	(8,004,730)	(4,497,921)	(3,955,438)
Originations and purchases of mortgage loans held-for-sale	(297,599)	0	0
Proceeds from sales of mortgage loans held-for-sale	7,624,799	4,484,838	4,076,887
BOLI income	(4,488)	(4,846)	(5,448)
Decrease (increase) in trading securities, net	397	624	(697)
Net (increase) decrease in brokerage customer receivables	(863)	(3,964)	13,822
Gains on mortgage loans sold	(339,127)	(135,607)	(104,998)
Losses (gains) on investment securities, net, and dividend reinvestment on equity securities	2,373	(3,525)	2,000
Losses on sales of premises and equipment, net	421	92	64
Net (gains) losses on sales and fair value adjustments of other real estate owned	(1,421)	1,921	4,664
Increase in accrued interest receivable and other assets, net	(131,870)	(133,022)	(133,519)
Increase (decrease) in accrued interest payable and other liabilities, net	46,924	(11,898)	(27,001)
Net Cash (Used for) Provided by Operating Activities	(518,465)	265,993	377,182
Investing Activities:
Proceeds from maturities and calls of available-for-sale securities	1,613,143	718,345	352,683
Proceeds from maturities and calls of held-to-maturity securities	879,713	422,959	11,129
Proceeds from sales of available-for-sale securities	502,250	972,253	214,196
Proceeds from sales of equity securities with readily determinable fair value	6,530	19,200	1,895
Proceeds from sales and capital distributions of equity securities without readily determinable fair value	1,857	1,764	1,324
Purchases of available-for-sale securities	(1,998,380)	(2,226,834)	(1,095,375)
Purchases of held-to-maturity securities	(125,220)	(493,389)	(253,129)
Purchases of equity securities with readily determinable fair value	(45,735)	(32,729)	0
Purchases of equity securities without readily determinable fair value	(5,118)	(4,394)	(4,592)
Purchase of Federal Home Loan Bank and Federal Reserve Bank stock, net	(34,849)	(9,385)	(1,365)
Distributions from investments in partnerships, net	76	1,955	3,409
Net cash paid in business combinations	0	(108,365)	(53,871)
Proceeds from sales of other real estate owned	10,776	14,516	19,375
Net increase in interest-bearing deposits with banks	(2,636,581)	(983,513)	(15,988)
Net increase in loans	(5,290,668)	(2,229,637)	(1,883,354)
Redemption of BOLI	3,428	326	8,438
Purchases of premises and equipment, net	(63,646)	(82,021)	(68,273)
Net Cash Used for Investing Activities	(7,182,424)	(4,018,949)	(2,763,498)
Financing Activities:
Increase in deposit accounts	6,985,964	3,142,499	2,547,399
Increase in other borrowings, net	88,596	15,480	137,257
Increase (decrease) in Federal Home Loan Bank advances, net	553,500	248,442	(147,999)
Cash payments to settle contingent consideration liabilities recognized in business combinations	(4,523)	(66)	0
Proceeds from the issuance of preferred stock, net	277,613	0	0
Proceeds from the issuance of subordinated notes, net	0	296,617	0
Issuance of common shares resulting from exercise of stock options, employee stock purchase plan and conversion of common stock warrants	15,059	10,667	15,903
Common stock repurchases under authorized program	(92,055)	0	0
Common stock repurchases for tax withholdings related to stock-based compensation	(1,377)	(1,297)	(648)
Dividends paid	(85,890)	(65,110)	(50,987)
Net Cash Provided by Financing Activities	7,736,887	3,647,232	2,500,925
Net Increase (Decrease) in Cash and Cash Equivalents	35,998	(105,724)	114,609
Cash and Cash Equivalents at Beginning of Period	286,476	392,200	277,591
Cash and Cash Equivalents at End of Period	322,474	286,476	392,200
Cash paid during the year for:
Interest	257,408	327,329	197,911
Income taxes, net	105,268	60,845	69,118
Business combinations and asset acquisitions:
Fair value of assets acquired, including cash and cash equivalents	0	1,093,254	485,368
Value ascribed to goodwill and other intangible assets	0	80,581	109,548
Fair value of liabilities assumed	0	896,686	423,234
Non-cash activities
Transfer to other real estate owned from loans	13,239	5,722	7,936
Common stock issued for acquisitions	$ 0	$ 71,756	$ 0