Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2017	$ 524,184	$ 102,947	$ 421,405	$ (168)
Balance, Shares at Dec. 31, 2017		24,052,000
Net income	14,466		14,466
Share-based compensation	864	$ 864
Common stock issued under stock Plans, net of shares withheld for employee taxes, Shares		50,000
Taxes paid related to net share settlement of stock awards	(971)	$ (971)
Dividends accrued of $0.375 and $1.36 per share for three months ended March 31 2019 and 2018	(8,237)		(8,237)
Other comprehensive loss	(22)			(22)
Balance at Mar. 31, 2018	530,284	$ 102,840	427,634	(190)
Balance, Shares at Mar. 31, 2018		24,102,000
Balance at Dec. 31, 2018	$ 571,535	$ 103,801	467,783	(49)
Balance, Shares at Dec. 31, 2018	24,182,000	24,182,000
Net income	$ 18,449		18,449
Share-based compensation	1,392	$ 1,392
Common stock issued under stock Plans, net of shares withheld for employee taxes, Shares		40,000
Taxes paid related to net share settlement of stock awards	(1,555)	$ (1,555)
Dividends accrued of $0.375 and $1.36 per share for three months ended March 31 2019 and 2018	(9,151)		(9,151)
Other comprehensive loss	(27)			(27)
Balance at Mar. 31, 2019	$ 580,643	$ 103,638	$ 477,081	$ (76)
Balance, Shares at Mar. 31, 2019	24,222,000	24,222,000