Consolidated Statements of Income and Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest income:
Interest and fees on loans, including loans held for sale	$ 128,457	$ 131,725	$ 137,653
Interest and dividends on securities:
Taxable	11,314	12,425	12,009
Tax exempt	2,576	2,249	2,074
Interest and dividends on Federal Reserve Bank and Federal Home Loan Bank stock	1,136	1,367	1,433
Other, including interest on federal funds sold	384	361	553
Total interest income	143,867	148,127	153,722
Interest expense:
Interest on deposits	9,798	11,313	17,911
Interest on repurchase agreements and other short-term borrowings	841	940	1,240
Interest on advances from Federal Home Loan Bank	27	26	34
Interest on long-term debt	1,131	1,161	2,403
Total interest expense	11,797	13,440	21,588
Net interest income	132,070	134,687	132,134
Provision for loan losses	8,755	8,568	9,450
Net interest income after provision for loan losses	123,315	126,119	122,684
Noninterest income:
Service charges on deposit accounts	23,892	24,650	23,996
Gains on sales of loans, net	1,468	3,098	2,562
Trust and wealth management income	9,011	8,199	6,918
Loan related fees	3,531	4,697	4,042
Bank owned life insurance	1,996	2,747	1,760
Brokerage revenue	2,454	2,245	2,209
Securities gains (losses)	(211)	(45)	1,155
Other noninterest income	2,940	3,713	3,315
Total noninterest income	45,081	49,304	45,957
Noninterest expense:
Officer salaries and employee benefits	11,076	10,432	10,561
Other salaries and employee benefits	43,417	42,411	41,327
Occupancy, net	8,017	7,804	7,546
Equipment	3,414	3,865	3,876
Data processing	7,877	7,308	6,394
Bank franchise tax	4,857	4,493	4,571
Legal fees	2,444	2,392	2,154
Professional fees	1,832	1,790	1,545
FDIC insurance	2,400	2,442	2,553
Other real estate owned provision and expense	3,897	5,154	5,267
Repossession expense	1,508	1,522	1,707
Other noninterest expense	15,260	20,638	16,053
Total noninterest expense	105,999	110,251	103,554
Income before income taxes	62,397	65,172	65,087
Income taxes	19,146	20,000	20,225
Net income	43,251	45,172	44,862
Unrealized holding gains (losses) on securities available-for-sale:
Unrealized holding gains (losses) arising during the period	13,928	(31,878)	4,973
Less: Reclassification adjustments for realized (gains) losses included in net income	211	45	(1,155)
Tax (benefit) expense	4,949	(11,142)	1,336
Other comprehensive income (loss), net of tax	9,190	(20,691)	2,482
Comprehensive income	$ 52,441	$ 24,481	$ 47,344
Basic earnings per share (in dollars per share)	$ 2.50	$ 2.63	$ 2.64
Diluted earnings per share (in dollars per share)	$ 2.49	$ 2.62	$ 2.63
Weighted average shares outstanding-basic (in shares)	17,326	17,158	17,013
Weighted average shares outstanding-diluted (in shares)	17,397	17,240	17,073
Dividends declared per share (in dollars per share)	$ 1.181	$ 1.154	$ 1.136