Consolidated Statements of Changes in Shareholders' Equity - USD ($)	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2013	$ 250,946,000	$ 89,356,000	$ 159,733,000	$ 1,857,000
Beginning balance, shares at Dec. 31, 2013		16,076,662
Net income	26,108,000		26,108,000
Other comprehensive income (loss)	(4,060,000)			(4,060,000)
Stock option vesting	965,000	$ 965,000
RSU vesting	126,000	126,000
PSU vesting	42,000	42,000
Stock options exercised	2,875,000	$ 2,875,000
Stock options exercised, shares		166,020
Tax effect of stock options exercised	225,000	$ 225,000
Issuance of common stock, value	151,303,000	$ 151,303,000
Issuance of common stock, shares		6,575,550
Repurchase of common stock, value	(2,551,000)	$ (574,000)	(1,977,000)
Repurchase of common stock, shares		(103,268)
Dividends paid	(7,807,000)		(7,807,000)
Ending balance at Dec. 31, 2014	418,172,000	$ 244,318,000	176,057,000	(2,203,000)
Ending balance, shares at Dec. 31, 2014		22,714,964
Net income	43,818,000		43,818,000
Other comprehensive income (loss)	425,000			425,000
Stock option vesting	734,000	$ 734,000
RSU vesting	457,000	457,000
PSU vesting	179,000	179,000
Stock options exercised	3,116,000	$ 3,116,000
Stock options exercised, shares		154,500
Tax effect of stock options exercised	83,000	$ 83,000
RSUs released		12,064
Tax benefit from release of RSUs	15,000	15,000
Repurchase of common stock, value	(2,868,000)	$ (1,149,000)	(1,719,000)
Repurchase of common stock, shares		(106,355)
Dividends paid	(11,849,000)		(11,849,000)
Ending balance at Dec. 31, 2015	$ 452,116,000	$ 247,587,000	206,307,000	(1,778,000)
Ending balance, shares at Dec. 31, 2015	22,775,173	22,775,173
Net income	$ 44,811,000		44,811,000
Other comprehensive income (loss)	(6,135,000)			(6,135,000)
Stock option vesting	580,000	$ 580,000
RSU vesting	616,000	616,000
PSU vesting	271,000	271,000
Stock options exercised	$ 6,506,000	$ 6,506,000
Stock options exercised, shares	336,900	336,900
Tax effect of stock options exercised	$ 154,000	$ 154,000
RSUs released		20,529
Tax benefit from release of RSUs	1,000	1,000
Repurchase of common stock, value	(7,878,000)	$ (2,895,000)	(4,983,000)
Repurchase of common stock, shares		(264,800)
Dividends paid	(13,695,000)		(13,695,000)
Ending balance at Dec. 31, 2016	$ 477,347,000	$ 252,820,000	$ 232,440,000	$ (7,913,000)
Ending balance, shares at Dec. 31, 2016	22,867,802	22,867,802