CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Non Controlling Interest	Total
Balance at Dec. 31, 2014	$ 5	$ 160,186	$ 293,628	$ (33)	$ 453,786
Balance (in shares) at Dec. 31, 2014	51,561,396
Increase (Decrease) in Stockholders' Equity Roll Forward
Net income			36,872	279	37,151
Issuance of shares to employees and directors		2,096			2,096
Issuance of shares to employees and directors (in shares)	114,744
Amortization of Restricted Stock Units		1,050			1,050
Dividend equivalent Units accrued - Restricted Stock Units		12	(12)
Distribution of non-controlling entities				(29)	(29)
Dividends declared			(10,589)		(10,589)
Balance at Dec. 31, 2015	$ 5	163,344	319,899	217	483,465
Balance (in shares) at Dec. 31, 2015	51,676,140
Increase (Decrease) in Stockholders' Equity Roll Forward
Net income			26,723	1,002	27,725
Issuance of shares to employees and directors		2,133			2,133
Issuance of shares to employees and directors (in shares)	108,102
Amortization of Restricted Stock Units		1,627			1,627
Dividend equivalent Units accrued - Restricted Stock Units		23	(23)
Repurchase of stock		(4,999)			(4,999)
Repurchase of stock (in shares)	(207,800)
Dividends declared			(11,381)		(11,381)
Balance at Dec. 31, 2016	$ 5	162,128	335,218	1,219	498,570
Balance (in shares) at Dec. 31, 2016	51,576,442
Increase (Decrease) in Stockholders' Equity Roll Forward
Net income			72,354	4,496	76,850
Issuance of shares to employees and directors		2,210			2,210
Issuance of shares to employees and directors (in shares)	88,661
Amortization of Restricted Stock Units		1,126			1,126
Dividend equivalent Units accrued - Restricted Stock Units		37	(37)
Repurchase of stock		(4,999)			(4,999)
Repurchase of stock (in shares)	(216,350)
Dividends declared			(11,574)		(11,574)
Balance at Dec. 31, 2017	$ 5	$ 160,502	$ 395,961	$ 5,715	$ 562,183
Balance (in shares) at Dec. 31, 2017	51,448,753