Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 40,554	$ 44,811	$ 43,818
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of premises and equipment, and amortization	6,787	6,474	5,906
Amortization of intangible assets	1,389	1,377	1,157
Provision for (benefit from reversal of) loan losses	89	(5,970)	(2,210)
Amortization of investment securities premium, net	3,200	4,926	3,458
Gain on sale of investment securities	(961)		0
Originations of loans for resale	(114,107)	(142,619)	(111,640)
Proceeds from sale of loans originated for resale	114,788	144,062	115,469
Gain on sale of loans	(3,109)	(4,037)	(3,064)
Change in market value of mortgage servicing rights	718	2,184	701
Provision for losses on foreclosed assets	162	140	502
Gain on sale of foreclosed assets	(711)	(262)	(991)
Provision for losses on fixed assets		782
Loss on disposal of fixed assets	142	147	129
Gain on sale of premises held for sale	(3)
Increase in cash value of life insurance	(2,685)	(2,717)	(2,786)
Gain on life insurance death benefit	(108)	(238)	(155)
Equity compensation vesting expense	1,586	1,467	1,370
Equity compensation tax effect		(155)	68
Deferred income tax expense	12,473	3,190	681
Change in:
Reserve for unfunded commitments	445	244	330
Interest receivable	(1,745)	(1,241)	(1,511)
Interest payable	112	44	(204)
Other assets and liabilities, net	(3,635)	(4,383)	3,789
Net cash from operating activities	55,381	48,226	54,817
Investing activities:
Proceeds from maturities of securities available for sale	63,942	71,684	33,552
Proceeds from sale of securities available for sale	25,757		2
Purchases of securities available for sale	(265,806)	(247,717)	(341,303)
Proceeds from maturities of securities held to maturity	86,371	121,666	93,784
Purchases of securities held to maturity			(146,100)
Loan origination and principal collections, net	(247,837)	(251,479)	(244,018)
Loans purchased	(11,567)	(22,503)
Proceeds from sale of loans other than loans originated for resale		37,880
Proceeds from sale of premises and equipment		1,682	8
Improvement of foreclosed assets			(195)
Proceeds from sale of other real estate owned	2,872	4,010	5,449
Proceeds from the sale of premises held for sale	3,338
Purchases of premises and equipment	(15,164)	(10,930)	(5,489)
Life insurance proceeds	649
Cash received from acquisition, net		156,316
Net cash used by investing activities	(357,445)	(139,391)	(604,310)
Financing activities:
Net increase in deposits	113,571	103,063	250,843
Net change in other borrowings	104,673	5,165	3,052
Equity compensation tax effect		155	(68)
Repurchase of common stock	(1,629)	(1,890)	(412)
Dividends paid	(15,131)	(13,695)	(11,849)
Exercise of stock options	396	518	660
Net cash from financing activities	201,880	93,316	242,226
Net change in cash and cash equivalents	(100,184)	2,151	(307,267)
Cash and cash equivalents and beginning of year	305,612	303,461	610,728
Cash and cash equivalents at end of year	205,428	305,612	303,461
Supplemental disclosure of noncash activities:
Unrealized loss on securities available for sale	5,461	(11,015)	(1,895)
Loans transferred to foreclosed assets	1,563	2,505	5,240
Due to broker			17,072
Market value of shares tendered in-lieu of cash to pay for exercise of options and/or related taxes	2,225	5,988	2,868
Supplemental disclosure of cash flow activity:
Cash paid for interest expense	5,609	5,677	5,620
Cash paid for income taxes	$ 21,170	27,575	$ 24,315
Assets acquired in acquisition		161,231
Liabilities assumed in acquisition		$ 161,231