CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Retained Earnings	Cost of Common Stock in Treasury	Accumulated Other Comprehensive Income (Loss), Net
Balance at Dec. 31, 2015	$ 644,053	$ 436,538	$ 251,812	$ (50,852)	$ 6,555
Increase (Decrease) in Shareholders' Equity
Net income	28,297		28,297
Other comprehensive income (loss)	4,276				4,276
Issuance of 60,459 and 104,853 common shares under stock based compensation awards for the six months ended on June 30, 2017 and 2016, respectively	2,504		4	2,500
Cost of 900 and 269,667 shares of common stock acquired for treasury for the six months ended on June 30, 2017 and 2016, respectively	(8,005)			(8,005)
Common stock dividend ($0.37 and $0.36 per share for the six months ended on June 30, 2017 and 2016, respectively)	(9,369)		(9,369)
Balance at Jun. 30, 2016	661,756	436,538	270,744	(56,357)	10,831
Balance at Dec. 31, 2016	672,650	436,538	290,824	(56,056)	1,344
Cumulative-effect adjustment at Dec. 31, 2016	(65)		(65)
Balance, adjusted at Dec. 31, 2016	672,585	436,538	290,759	(56,056)	1,344
Increase (Decrease) in Shareholders' Equity
Net income	32,875		32,875
Other comprehensive income (loss)	1,093				1,093
Issuance of 60,459 and 104,853 common shares under stock based compensation awards for the six months ended on June 30, 2017 and 2016, respectively	2,305		870	1,435
Cost of 900 and 269,667 shares of common stock acquired for treasury for the six months ended on June 30, 2017 and 2016, respectively	(41)			(41)
Common stock dividend ($0.37 and $0.36 per share for the six months ended on June 30, 2017 and 2016, respectively)	(9,615)		(9,615)
Balance at Jun. 30, 2017	$ 699,202	$ 436,538	$ 314,889	$ (54,662)	$ 2,437