Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities:
Net income	$ 343,166	$ 257,682	$ 206,875
Adjustments to reconcile net income to net cash provided by operating activities
Provision for credit losses	34,832	29,768	34,084
Depreciation, amortization and accretion, net	67,665	63,107	53,148
Deferred income tax expense	55,224	63,243	6,676
Stock-based compensation expense	13,496	12,858	9,303
Net amortization of premium on securities	7,411	6,098	5,646
Accretion of discounts on loans	(20,318)	(22,784)	(35,571)
Mortgage servicing rights fair value change, net	5,370	1,857	3,405
Originations and purchases of mortgage loans held-for-sale	(3,955,438)	(3,692,085)	(4,386,339)
Proceeds from sales of mortgage loans held-for-sale	4,076,887	3,869,137	4,468,984
BOLI income	(5,448)	(3,524)	(3,594)
(Increase) decrease in trading securities, net	(697)	994	(1,541)
Net decrease (increase) in brokerage customer receivables	13,822	(1,250)	2,450
Gains on mortgage loans sold	(104,998)	(88,699)	(112,981)
Losses (gains) on investment securities, net, and dividend reinvestment on equity securities	2,000	(45)	(7,645)
Gains on early extinguishment of debt, net	0	0	(3,588)
Losses (gains) on sales of premises and equipment, net	64	(192)	(305)
Net losses on sales and fair value adjustments of other real estate owned	4,664	639	1,381
Gain on termination of loss share agreements with the FDIC	0	(385)	0
Increase in accrued interest receivable and other assets, net	(133,519)	(126,583)	(43,953)
(Decrease) increase in accrued interest payable and other liabilities, net	(27,001)	31,790	114,531
Net Cash Provided by Operating Activities	377,182	401,626	310,966
Investing Activities:
Proceeds from maturities and calls of available-for-sale securities	352,683	276,097	1,247,894
Proceeds from maturities and calls of held-to-maturity securities	11,129	108,943	735,036
Proceeds from sales of available-for-sale securities	214,196	344,674	2,194,278
Proceeds from sales of equity securities with readily determinable fair value	1,895	0	0
Proceeds from sales and capital distributions of equity securities without readily determinable fair value	1,324	0	0
Purchases of available-for-sale securities	(1,095,375)	(774,041)	(3,398,640)
Purchases of held-to-maturity securities	(253,129)	(301,909)	(486,696)
Purchases of equity securities without readily determinable fair value	(4,592)	0	0
(Purchase) redemption of Federal Home Loan Bank and Federal Reserve Bank stock, net	(1,365)	43,505	(31,913)
Distributions from investments in partnerships, net	3,409	512	339
Net cash paid in business combinations	(53,871)	(284)	(613,619)
Proceeds from sales of other real estate owned	19,375	18,742	38,367
Proceeds (paid to) received from the FDIC related to reimbursements on covered assets	0	(15,411)	1,207
Net increase in interest-bearing deposits with banks	(15,988)	(81,621)	(366,591)
Net increase in loans	(1,883,354)	(1,863,245)	(1,779,905)
Redemption of BOLI	8,438	0	1,840
Purchases of premises and equipment, net	(68,273)	(59,194)	(33,923)
Net Cash Used for Investing Activities	(2,763,498)	(2,303,232)	(2,492,326)
Financing Activities:
Increase in deposit accounts	2,547,399	1,524,848	2,769,022
Increase (decrease) in subordinated notes and other borrowings, net	137,257	(4,888)	(3,405)
(Decrease) increase in Federal Home Loan Bank advances, net	(147,999)	403,000	(707,594)
Cash payments to settle contingent consideration liabilities recognized in business combinations	0	(1,097)	(1,273)
Proceeds from the issuance of common stock, net	0	0	152,911
Redemption of junior subordinated debentures, net	0	0	(10,695)
Issuance of common shares resulting from exercise of stock options, employee stock purchase plan and conversion of common stock warrants	15,903	28,229	15,828
Common stock repurchases for tax withholdings related to stock-based compensation	(648)	(397)	(616)
Dividends paid	(50,987)	(40,543)	(38,568)
Net Cash Provided by Financing Activities	2,500,925	1,909,152	2,175,610
Net Increase (Decrease) in Cash and Cash Equivalents	114,609	7,546	(5,750)
Cash and Cash Equivalents at Beginning of Period	277,591	270,045	275,795
Cash and Cash Equivalents at End of Period	392,200	277,591	270,045
Cash paid during the year for:
Interest	197,911	112,783	91,390
Income taxes, net	69,118	76,812	94,888
Business combinations and asset acquisitions:
Fair value of assets acquired, including cash and cash equivalents	485,368	1,022	882,865
Value ascribed to goodwill and other intangible assets	109,548	999	27,083
Fair value of liabilities assumed	423,234	738	259,631
Non-cash activities
Transfer to other real estate owned from loans	7,936	15,013	13,352
Common stock issued for acquisitions	$ 0	$ 0	$ 0