Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net income	$ 38,043	$ 41,027	$ 37,187
Adjustments to reconcile net income to net cash provided by operating activities:
Provision (credit) for loan losses	2,550	3,000	750
Depreciation, amortization and accretion, net	13,640	11,142	6,902
Deferred income tax expense (benefit)	3,971	276	847
Loss on sale of securities available-for-sale	232
Impairment loss on available-for-sale securities	0		103
Gains on sales of mortgage loans held for sale	(1,989)	(2,482)	(2,167)
Origination of mortgage loans held for sale	(97,623)	(123,347)	(116,385)
Proceeds from sale of mortgage loans held for sale	99,861	129,416	115,499
Bank owned life insurance income	(1,159)	(871)	(889)
Proceeds from liquidation of private investment fund	(92)
(Gain) Loss on other real estate owned	(39)	(409)	147
Loss (gain) on the disposal of premises and equipment		202	(51)
Recovery of impairment loss on other assets held for investment		(588)
Stock compensation expense	2,892	2,473	2,134
Excess tax benefits from share-based compensation arrangements	(1,463)	(1,705)	(673)
Increase in accrued interest receivable and other assets	(13,848)	(7,438)	(2,540)
Increase in accrued interest payable and other liabilities	8,700	12,566	2,307
Net cash provided by operating activities	53,676	63,262	43,171
Investing activities
Purchases of securities available-for-sale	(661,086)	(478,798)	(384,260)
Proceeds from sale of securities available-for-sale	421	0	5,934
Proceeds from maturities of securities available-for-sale	652,411	468,271	320,952
Purchase of Federal Home Loan Bank Stock	(2,254)
Proceeds from sale of Federal Home Loan Bank stock	955
Proceeds from liquidation of private investment fund	92
Net increase in loans	(105,867)	(275,718)	(168,832)
Purchases of premises and equipment	(2,786)	(6,327)	(3,459)
Proceeds from disposal of equipment		66
Proceeds from mortality benefit of bank owned life insurance	977
Proceeds from sale of other real estate owned	2,432	1,826	2,541
Proceeds from the sale of other assets held for investment		1,108
Net cash used in investing activities	(114,705)	(289,572)	(227,124)
Financing activities
Net increase in deposits	57,747	148,846	248,075
Net increase (decrease) in securities sold under agreements to repurchase and federal funds purchased	116,856	27,966	(29,946)
Proceeds from Federal Home Loan Bank advances	120,000	289,000	108,200
Repayments of Federal Home Loan Bank advances	(121,617)	(281,393)	(101,564)
Proceeds (used for) and received from settlement of stock awards	(216)	2,337	3,249
Excess tax benefits from share-based compensation arrangements		1,705	673
Common stock repurchases	(2,389)	(1,918)	(918)
Cash dividends paid	(18,077)	(16,093)	(14,224)
Net cash provided by financing activities	152,304	170,450	213,545
Net increase (decrease) in cash and cash equivalents	91,275	(55,860)	29,592
Cash and cash equivalents at beginning of year	47,973	103,833	74,241
Cash and cash equivalents at end of period	$ 139,248	$ 47,973	$ 103,833