Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2014	$ 418,172	$ 244,318	$ 176,057	$ (2,203)
Beginning balance, shares at Dec. 31, 2014		22,714,964
Net income	19,702		19,702
Other comprehensive income (loss)	(2,523)			(2,523)
Stock option vesting	419	$ 419
RSU vesting	202	202
PSU vesting	77	77
Stock options exercised	1,236	$ 1,236
Stock options exercised, shares		64,000
Tax effect of stock option exercise	30	$ 30
Repurchase of common stock	(698)	$ (317)	(381)
Repurchase of common stock, shares		(29,441)
Dividends paid	(5,473)		(5,473)
Ending balance at Jun. 30, 2015	431,144	$ 245,965	189,905	(4,726)
Ending balance, shares at Jun. 30, 2015		22,749,523
Beginning balance at Dec. 31, 2015	$ 452,116	$ 247,587	206,307	(1,778)
Beginning balance, shares at Dec. 31, 2015	22,775,173	22,775,173
Net income	$ 20,079		20,079
Other comprehensive income (loss)	7,851			7,851
Stock option vesting	311	$ 311
RSU vesting	261	261
PSU vesting	125	125
Stock options exercised	$ 2,814	$ 2,814
Stock options exercised, shares	127,200	127,200
RSUs released	$ 0	$ 0	0	0
RSUs released, shares		16,948
Tax effect of stock option exercise	(192)	$ (192)
Tax effect of RSU release	10	10
Repurchase of common stock	(2,666)	$ (1,056)	(1,610)
Repurchase of common stock, shares		(96,996)
Dividends paid	(6,841)		(6,841)
Ending balance at Jun. 30, 2016	$ 473,868	$ 249,860	$ 217,935	$ 6,073
Ending balance, shares at Jun. 30, 2016	22,822,325	22,822,325