Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Restricted Stock Awards Repurchased to Satisfy Tax Obligations [Member] Retained Earnings [Member]	Restricted Stock Awards Repurchased to Satisfy Tax Obligations [Member] Treasury Stock [Member]	Restricted Stock Awards Repurchased to Satisfy Tax Obligations [Member]	Shares Purchased to Fund Options Exercised [Member] Retained Earnings [Member]	Shares Purchased to Fund Options Exercised [Member] Treasury Stock [Member]	Shares Purchased to Fund Options Exercised [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Dec. 31, 2015							$ 315	$ 210,652	$ 316,530	$ (48,868)	$ (5,562)	$ 473,067
Net income									9,561			9,561
Award of common shares released from Employee Benefit Trust								1,851				1,851
Vesting of restricted stock unit awards								(4,047)	(396)	4,443
Stock-based compensation expense								2,960				2,960
Purchase of treasury shares		$ (1,582)	$ (1,582)		$ (303)	$ (303)
Dividends on common stock									(4,970)			(4,970)
Other comprehensive income											6,873	6,873
Balance at Mar. 31, 2016							315	211,735	320,725	(46,307)	1,311	487,779
Exercise of stock options								16		3		19
Stock-based income tax benefit								303				303
Balance at Dec. 31, 2016							315	214,462	361,192	(53,754)	(8,362)	513,853
Net income									12,260			12,260
Award of common shares released from Employee Benefit Trust								2,280				2,280
Vesting of restricted stock unit awards								(4,536)	(262)	4,798
Stock-based compensation expense								3,295				3,295
Purchase of treasury shares		$ (2,268)	$ (2,268)
Dividends on common stock									(5,246)			(5,246)
Other comprehensive income											1,228	1,228
Balance at Mar. 31, 2017							$ 315	$ 215,501	$ 367,944	$ (51,224)	$ (7,134)	$ 525,402