Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Number of Common Shares	Common Stock	Retained Earnings	Paid-in Capital	Accumulated Other Comprehensive Income(Loss)
Balance, shares at Dec. 31, 2015		19,290,000
Balance at Dec. 31, 2015	$ 333,260		$ 19	$ 378,321	$ (42,286)	$ (2,794)
Net income	47,971			47,971
Other comprehensive income (loss), net of tax	1,310					1,310
Adjustments to Additional Paid in Capital, Share-based Compensation, Stock Options, Requisite Service Period Recognition	(1,428)				(1,428)
Proceeds from stock award exercises and issuances		192,000
Share-based compensation	3,732				3,732
Excess tax benefits from exercise of stock options	(9)				(9)
Common stock repurchases		(27,000)
Restricted stock forfeitures	(366)				(366)
Dividends declared	$ (37,244)			(37,244)
Balance, shares at Dec. 31, 2016	19,455,011	19,455,000
Balance at Dec. 31, 2016	$ 347,226		19	389,048	(40,357)	(1,484)
Net income	10,923			10,923
Other comprehensive income (loss), net of tax	87					87
Adjustments to Additional Paid in Capital, Share-based Compensation, Stock Options, Requisite Service Period Recognition	(902)				(902)
Proceeds from stock award exercises and issuances		28,000
Share-based compensation	717				717
Common stock repurchases		(8,000)
Restricted stock forfeitures	(360)				(360)
Dividends declared	$ (9,369)			(9,369)
Balance, shares at Mar. 31, 2017	194,750,127	19,475,000
Balance at Mar. 31, 2017	$ 348,322		$ 19	$ 390,602	$ (40,902)	$ (1,397)