Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest income:
Interest and fees on loans, including loans held for sale	$ 133,965	$ 130,829	$ 128,457
Interest and dividends on securities:
Taxable	8,265	9,153	11,314
Tax exempt	2,718	2,705	2,576
Interest and dividends on Federal Reserve Bank and Federal Home Loan Bank stock	1,011	1,010	1,136
Other, including interest on federal funds sold	617	323	384
Total interest income	146,576	144,020	143,867
Interest expense:
Interest on deposits	10,921	9,616	9,798
Interest on repurchase agreements	1,155	938	841
Interest on advances from Federal Home Loan Bank	62	49	27
Interest on long-term debt	1,417	1,170	1,131
Total interest expense	13,555	11,773	11,797
Net interest income	133,021	132,247	132,070
Provision for loan losses	7,872	8,650	8,755
Net interest income after provision for loan losses	125,149	123,597	123,315
Noninterest income:
Service charges on deposit accounts	24,966	24,282	23,892
Gains on sales of loans, net	1,831	1,978	1,468
Trust and wealth management income	9,585	9,286	9,011
Loan related fees	4,107	3,821	3,531
Bank owned life insurance	2,199	2,158	1,996
Brokerage revenue	1,314	1,426	2,454
Securities gains (losses)	522	(106)	(211)
Other noninterest income	3,917	3,964	2,940
Total noninterest income	48,441	46,809	45,081
Noninterest expense:
Officer salaries and employee benefits	12,198	11,652	11,076
Other salaries and employee benefits	44,877	42,911	43,417
Occupancy, net	7,999	7,826	8,017
Equipment	2,950	3,049	3,414
Data processing	6,497	6,743	7,877
Bank franchise tax	5,671	5,174	4,857
Legal fees	1,906	2,236	2,444
Professional fees	1,890	1,884	1,832
Advertising and marketing	2,614	2,428	2,421
FDIC insurance	1,789	2,382	2,400
Other real estate owned provision and expense	2,879	3,533	3,897
Repossession expense	1,156	1,265	1,508
Amortization of limited partnership investments	2,623	2,580	859
Other noninterest expense	12,077	11,780	11,980
Total noninterest expense	107,126	105,443	105,999
Income before income taxes	66,464	64,963	62,397
Income taxes	19,118	18,531	19,146
Net income	47,346	46,432	43,251
Unrealized holding gains (losses) on securities available-for-sale:
Unrealized holding gains (losses) arising during the period	(4,578)	(342)	13,928
Less: Reclassification adjustments for realized gains (losses) included in net income	522	(106)	(211)
Tax expense (benefit)	(1,785)	(83)	4,949
Other comprehensive income (loss), net of tax	(3,315)	(153)	9,190
Comprehensive income	$ 44,031	$ 46,279	$ 52,441
Basic earnings per share (in dollars per share)	$ 2.70	$ 2.66	$ 2.50
Diluted earnings per share (in dollars per share)	$ 2.70	$ 2.66	$ 2.49
Weighted average shares outstanding-basic (in shares)	17,548	17,431	17,326
Weighted average shares outstanding-diluted (in shares)	17,566	17,483	17,397
Dividends declared per share (in dollars per share)	$ 1.260	$ 1.220	$ 1.181