Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities
Net income		$ 157,870	$ 98,387	$ 92,349
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses		47,854	31,290	30,983
Depreciation of premises, furniture, and equipment		15,865	13,995	12,804
Net amortization of premium on securities		15,348	16,142	13,653
Net securities losses (gains)		0
Net securities losses (gains)			1,876	(1,420)
Gains on sales of 1-4 family mortgages and corporate loans held-for-sale		(5,562)	(7,078)	(8,931)
Net (gains) losses on sales and valuation adjustments of OREO		(347)	585	1,196
Amortization of the FDIC indemnification asset		1,208	1,208	1,185
Net losses (gains)		5,227	(125)	(4,762)
BOLI income		(5,835)	(5,946)	(3,647)
Net pension cost (income)		1,447	981	(513)
Share-based compensation expense	[1]	12,062	11,223	7,879
Tax benefit (expense) related to share-based compensation		258	349	(197)
Provision for deferred income tax expense (benefit)		26,309	(4,077)	(1,367)
Amortization of other intangible assets		7,444	7,865	4,682
Originations of mortgage loans held-for-sale		(224,303)	(254,030)	(238,192)
Proceeds from sales of mortgage loans held-for-sale		245,967	258,626	246,642
Net decrease in equity securities		964	0	0
Net increase in trading securities		0	(2,527)	(1,026)
Net (increase) decrease in accrued interest receivable and other assets		(44,246)	121,577	(76,902)
Net (decrease) increase in accrued interest payables and other liabilities		(4,346)	(56,055)	47,315
Net cash provided by operating activities		253,184	234,266	121,731
Investing Activities
Proceeds from maturities, repayments, and calls of securities available-for-sale		331,026	349,444	360,303
Proceeds from sales of securities available-for-sale		24,974	629,843	53,186
Purchases of securities available-for-sale		(735,701)	(733,440)	(933,317)
Proceeds from maturities, repayments, and calls of securities held-to-maturity		3,584	8,546	8,077
Purchases of securities held-to-maturity		0	(15)	(5,352)
Net purchases of FHLB stock		(10,040)	(7,330)	(18,276)
Net increase in loans		(770,039)	(457,501)	(714,213)
Proceeds from claims on BOLI, net of premiums paid		(49)	1,722	1,588
Proceeds from sales of OREO		16,953	19,326	7,539
Proceeds from sales of premises, furniture, and equipment		4,561	18,031	152,863
Purchases of premises, furniture, and equipment		(27,800)	(16,123)	(19,083)
Net cash received from acquisitions		160,145	41,717	57,347
Net cash used in investing activities		(1,002,386)	(145,780)	(1,049,338)
Financing Activities
Net increase in deposit accounts		567,627	200,848	135,944
Net increase (decrease) in borrowed funds		172,977	(164,124)	711,496
Net proceeds from the issuance of subordinated debt		0	0	146,484
Payments for the retirement of senior and subordinated debt		0	0	(153,500)
Cash dividends paid		(44,293)	(37,129)	(29,198)
Restricted stock activity		(4,421)	(3,659)	(2,673)
Net cash provided by (used in) financing activities		691,890	(4,064)	808,553
Net (decrease) increase in cash and cash equivalents		(57,312)	84,422	(119,054)
Cash and cash equivalents at beginning of year		346,570	262,148	381,202
Cash and cash equivalents at end of year		289,258	346,570	262,148
Supplemental Disclosures of Cash Flow Information:
Income taxes (refunded) paid		(1,108)	15,191	57,553
Interest paid to depositors and creditors		60,569	36,424	27,400
Dividends declared, but unpaid			10,185	7,243
Common stock issued for acquisitions, net of issuance costs		83,303	534,090	54,896
Non-cash transfers of loans to OREO		6,027	6,255	4,173
Non-cash transfers of loans held-for-investment to loans held-for-sale		15,060	48,999	93,981
Non-cash transfer of trading securities and securities available-for-sale to equity securities		$ 27,855	$ 0	$ 0

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