Condensed Consolidated Statements of Cash Flows - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 87,554,000	$ 101,282,000	$ 99,473,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	28,704,000	21,582,000	21,470,000
Provision for loan losses	11,890,000	6,819,000	5,864,000
Deferred income taxes	5,640,000	9,378,000	7,048,000
Write Down In Deferred Tax Asset Due To Tax Rate Changes	26,558,000
Other-than-temporary impairment on securities	753,000		489,000
(Gain) loss on sale of securities, net	(1,421,000)	(122,000)
Share-based compensation expense	6,934,000	6,220,000	5,803,000
Amortization on FDIC indemnification asset		3,566,000	8,587,000
Accretion of discount related to performing acquired loans	(15,893,000)	(5,187,000)	(6,638,000)
(Gain) Loss on disposals of premises and equipment	177,000	(60,000)	576,000
Gain on sale of OREO	101,000	(1,735,000)	(1,674,000)
Net amortization of premium on investment securities	6,853,000	5,409,000	4,415,000
OREO Write downs	2,249,000	4,401,000	9,428,000
Fair Value adjustment for loans held for sale	752,000	495,000	515,000
Originations and purchases of mortgage loans for sale	(682,403,000)	(771,105,000)	(844,401,000)
Proceeds from mortgage loans sales	745,871,000	761,688,000	864,171,000
Net change in:
Accrued interest receivable	(2,198,000)	(1,536,000)	(717,000)
Prepaid assets	6,000	(804,000)	(876,000)
FDIC indemnification asset		3,177,000	9,173,000
Miscellaneous other assets	(32,324,000)	(13,799,000)	(4,861,000)
Accrued interest payable	(948,000)	(831,000)	(2,121,000)
Accrued income taxes	1,959,000	105,000	13,095,000
Miscellaneous other liabilities	7,076,000	9,068,000	(1,951,000)
Net cash provided by operating activities	197,890,000	138,011,000	186,868,000
Cash flows from investing activities:
Proceeds from sales of investment securities available for sale	374,938,000	137,000
Proceeds from maturities and calls of investment securities held to maturity	3,570,000	3,225,000	345,000
Proceeds from maturities and calls of investment securities available for sale	235,757,000	383,577,000	223,750,000
Proceeds from calls of other investment securities			1,392,000
Proceeds from sales of other investment securities	15,302,000	71,000	233,000
Purchases of investment securities available for sale	(241,274,000)	(385,813,000)	(436,081,000)
Purchases of other investment securities	(4,553,000)	(660,000)
Net increase in loans	(636,836,000)	(690,495,000)	(318,936,000)
Payment to terminate FDIC Loss Share Agreements		(2,342,000)
Recoveries of loans previously charged off	3,430,000	3,552,000	2,800,000
Net cash received from acquisitions	185,163,000		403,548,000
Purchases of premises and equipment	(15,163,000)	(25,796,000)	(15,225,000)
Proceeds from sale of OREO	18,751,000	23,565,000	35,120,000
Proceeds from sale of premises and equipment	15,000	60,000	39,000
Net cash provided by (used in) investing activities	(60,900,000)	(690,919,000)	(103,015,000)
Cash flows from financing activities:
Net increase (decrease) in deposits	226,045,000	233,993,000	201,097,000
Net increase in federal funds purchased and securities sold under agreements to repurchase and other short-term borrowings	(27,930,000)	25,542,000	66,691,000
Proceeds from FHLB advances	100,000,000
Repayment of other borrowings	(390,811,000)	(14,000)	(46,398,000)
Common stock issuance	1,055,000	925,000	908,000
Common stock repurchase	(5,512,000)	(5,981,000)	(5,631,000)
Dividends paid on common stock	(38,623,000)	(29,285,000)	(23,710,000)
Excess tax benefits in connection with equity awards		4,178,000
Stock options exercised	1,965,000	2,204,000	1,115,000
Net cash provided by financing activities	(133,811,000)	231,562,000	194,072,000
Net increase (decrease) in cash and cash equivalents	3,179,000	(321,346,000)	277,925,000
Cash and cash equivalents at beginning of period	374,448,000	695,794,000	417,869,000
Cash and cash equivalents at end of period	377,627,000	374,448,000	695,794,000
Cash paid for:
Interest	17,962,000	9,148,000	12,449,000
Income taxes	48,028,000	39,490,000	31,375,000
Acquisitions:
Fair value of tangible assets acquired	4,900,334,000		435,912,000
Other intangible assets acquired	44,295,000		6,800,000
Liabilities assumed	4,477,801,000		438,345,000
Net identifiable assets acquired over (under) liabilities assumed	$ 466,828,000		4,367,000
Common stock issued in acquisition	1,123,175
Loans sold that have not settled	$ 28,663,000
Real estate acquired in full or in partial settlement of loans	$ 11,558,000	$ 13,993,000	$ 30,702,000