UNAUDITED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2014	$ 29,712	$ 227,512	$ 1,122	$ 258,346
Balance (in shares) at Dec. 31, 2014	48,265
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	40,864	0	40,864
Other comprehensive loss, net of tax	0	0	(707)	(707)
Dividends declared ($0.24 per share)	0	(11,629)	0	(11,629)
Dividends reinvested in common stock	$ 544	0	0	544
Dividends reinvested in common stock (in shares)	22
Stock based compensation	$ 2,719	0	0	2,719
Common stock issued through exercise of incentive stock options	$ 996	0	0	996
Common stock issued through exercise of incentive stock options (in shares)	87
Common stock issued for share awards	$ 0	0	0	0
Common stock issued for share awards (in shares)	212
Common stock issued	$ 11	0	0	11
Common stock issued (in shares)	1
Common stock repurchased	$ (1,885)	0	0	(1,885)
Common stock repurchased (in shares)	(111)
Net excess tax benefit from stock options exercised	$ 679	0	0	679
Balance at Dec. 31, 2015	$ 32,776	256,747	415	289,938
Balance (in shares) at Dec. 31, 2015	48,475
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	13,881	0	13,881
Other comprehensive loss, net of tax	0	0	(1,048)	(1,048)
Stock based compensation	1,215	0	0	1,215
Common stock issued through exercise of incentive stock options	$ 2,806	0	0	2,806
Common stock issued through exercise of incentive stock options (in shares)	298
Common stock issued for share awards	$ 0	0	0	0
Common stock issued for share awards (in shares)	156
Common stock issued	$ 3	0	0	3
Common stock issued (in shares)	1
Common stock repurchased	$ (3,526)	0	0	(3,526)
Common stock repurchased (in shares)	(161)
Balance at Mar. 31, 2016	$ 33,274	$ 270,628	$ (633)	$ 303,269
Balance (in shares) at Mar. 31, 2016	48,769