Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income		$ 199,738	$ 157,870	$ 98,387
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses		44,027	47,854	31,290
Depreciation of premises, furniture, and equipment		16,366	15,865	13,995
Net amortization of premium on securities		15,731	15,348	16,142
Net securities losses		0	0
Net securities losses				1,876
Gains on sales of 1-4 family mortgages and corporate loans held-for-sale		(9,992)	(5,562)	(7,078)
Net losses (gains) on sales and valuation adjustments of OREO		373	(347)	585
Amortization of the FDIC indemnification asset		1,208	1,208	1,208
Net losses (gains) on sales and valuation adjustments of premises, furniture, and equipment		879	5,227	(125)
BOLI income		(8,394)	(5,835)	(5,946)
Net pension (income) cost		(489)	1,447	981
Share-based compensation expense	[1]	13,183	12,062	11,223
Tax benefit related to share-based compensation		364	258	349
Provision for deferred income tax expense (benefit)		10,944	26,309	(4,077)
Amortization of other intangible assets		10,481	7,444	7,865
Originations of mortgage loans held-for-sale		(499,318)	(224,303)	(254,030)
Proceeds from sales of mortgage loans held-for-sale		474,384	245,967	258,626
Net (increase) decrease in equity securities		(4,364)	964	0
Net increase in trading securities		0	0	(2,527)
Net (increase) decrease in accrued interest receivable and other assets		(146,968)	(44,246)	121,577
Net increase (decrease) in accrued interest payables and other liabilities		108,956	(4,346)	(56,055)
Net cash provided by operating activities		227,109	253,184	234,266
Investing Activities
Proceeds from maturities, repayments, and calls of securities available-for-sale		531,032	331,026	349,444
Proceeds from sales of securities available-for-sale		93,332	24,974	629,843
Purchases of securities available-for-sale		(916,564)	(735,701)	(733,440)
Proceeds from maturities, repayments, and calls of securities held-to-maturity		4,460	3,584	8,546
Purchases of securities held-to-maturity		(2,855)	0	(15)
Net purchases of FHLB stock		(33,626)	(10,040)	(7,330)
Net increase in loans		(719,676)	(770,039)	(457,501)
Proceeds from claims on BOLI, net of premiums paid		8,776		1,722
Proceeds from claims on BOLI, net of premiums paid			(49)
Proceeds from sales of OREO		10,645	16,953	19,326
Proceeds from sales of premises, furniture, and equipment		4,145	4,561	18,031
Purchases of premises, furniture, and equipment		(20,330)	(27,800)	(16,123)
Net cash (paid for) received from acquisitions		(13,532)
Net cash (paid for) received from acquisitions			160,145	41,717
Net cash used in investing activities		(1,054,193)	(1,002,386)	(145,780)
Financing Activities
Net increase in deposit accounts		180,412	567,627	200,848
Net increase (decrease) in borrowed funds		750,933	172,977
Net increase (decrease) in borrowed funds				(164,124)
Repurchases of common stock		33,928	0	0
Cash dividends paid		(56,540)	(44,293)	(37,129)
Restricted stock activity		(3,830)	(4,421)	(3,659)
Net cash provided by (used in) financing activities		837,047	691,890	(4,064)
Net increase (decrease) in cash and cash equivalents		9,963	(57,312)	84,422
Cash and cash equivalents at beginning of year		289,258	346,570	262,148
Cash and cash equivalents at end of year		299,221	289,258	346,570
Supplemental Disclosures of Cash Flow Information:
Income taxes paid (refunded)		48,899	(1,108)	15,191
Interest paid to depositors and creditors		109,760	60,569	36,424
Dividends declared, but unpaid		15,283	12,674	10,185
Common stock issued for acquisitions, net of issuance costs		101,496	83,303	534,090
Non-cash transfers of loans to OREO		944	6,027	6,255
Non-cash transfers of loans to other assets		13,175	0	0
Non-cash transfers of loans held-for-investment to loans held-for-sale		9,472	15,060	48,999
Non-cash transfer of trading securities and securities available-for-sale to equity securities		0	$ 27,855	$ 0
Non-cash recognition of right-of-use asset		$ 143,561

[1] Comprised of restricted stock, restricted stock unit, and performance share awards expense.