Consolidated Statements Of Changes In Shareholders' Equity - USD ($)		Total	Common Stock		Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance (in shares) at Dec. 31, 2014			11,139,333
Beginning Balance at Dec. 31, 2014		$ 245,109,000	$ 41,555,000		$ 211,979,000	$ (8,425,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		20,952,000			20,952,000
Other comprehensive loss, net of tax		(3,797,000)				(3,797,000)
Stock-based compensation expense		836,000	$ 836,000
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)			66,741
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings		753,000	$ 753,000
Common stock repurchased (in shares)			0
Equity issuance costs incurred for the SBM Financial, Inc. acquisition		(612,000)	$ (612,000)
Cash dividends declared ( $0.74, $0.80 and $0.83 per share in 2016, 2015, and 2014, respectively)	[1]	(10,602,000)			(10,602,000)
Equity issuance costs		(612,000)
SBM acquisition common stock issuance (in shares)			4,124,643
SBM acquisition common stock issuance		108,561,000	$ 108,561,000
SBM acquisition non-qualified stock option awards		1,990,000	$ 1,990,000
Ending Balance (in shares) at Dec. 31, 2015			15,330,717
Ending Balance at Dec. 31, 2015		363,190,000	$ 153,083,000		222,329,000	(12,222,000)
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income			$ 72,000	[1]	(72,000)
Stock Issued During Period, Shares, Stock Splits			(173)
Stockholders' Equity Note, Stock Split, Reduction of Capital		(5,000)	$ (5,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		40,067,000			40,067,000
Other comprehensive loss, net of tax		(1,687,000)				(1,687,000)
Stock-based compensation expense		1,997,000	$ 1,997,000
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)			145,835
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings		894,000	$ 894,000
Cash dividends declared ( $0.74, $0.80 and $0.83 per share in 2016, 2015, and 2014, respectively)	[1]	(12,909,000)			(12,909,000)
Equity issuance costs		0
Ending Balance (in shares) at Dec. 31, 2016			15,476,379.000
Ending Balance at Dec. 31, 2016		391,547,000	$ 156,041,000		249,415,000	(13,909,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		28,476,000			28,476,000
Reclassification from AOCI, Current Period, Tax	[2]				3,476,000	(3,476,000)
Other comprehensive loss, net of tax		(2,829,000)				(2,829,000)
Stock-based compensation expense		1,469,000	$ 1,469,000
Exercise of stock options and issuance of restricted stock, net of repurchase for tax withholdings and tax benefit (in shares)			48,325
Exercise of stock options and issuance of vested share awards, net of repurchase for tax withholdings		(606,000)	$ (606,000)
Cash dividends declared ( $0.74, $0.80 and $0.83 per share in 2016, 2015, and 2014, respectively)	[1]	(14,644,000)			(14,644,000)
Equity issuance costs		0
Ending Balance (in shares) at Dec. 31, 2017			15,524,704.000
Ending Balance at Dec. 31, 2017		$ 403,413,000	$ 156,904,000		$ 266,723,000	$ (20,214,000)

[1] In the second quarter of 2016, the Company adopted ASU 2016-09, effective January 1, 2016. The Company made a policy election to not estimate the forfeiture rate in the accounting for share-based compensation on its unvested share-based awards. The change in policy was accounted for on a modified-retrospective basis and represents the cumulative effect adjustment to shareholders' equity.

[2] In December of 2017, the Company early adopted ASU 2018-02, as a result, the Company made a policy election to release income tax effects, as a result of the Tax Act, from AOCI to retained earnings.