Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Earnings	Accumulated Other Comprehensive Loss	Non-Controlling Interest
Beginning balance (in shares) at Dec. 31, 2014		77,893,144
Beginning balance at Dec. 31, 2014	$ 94,840	$ 779	$ 59,740	$ 40,843	$ (6,522)	$ 0
Share-based compensation recognized	$ 5,204		5,204
Repurchase of common stock (in shares)	(3,000,000)	(3,012,826)
Repurchase of common stock	$ (54,949)	$ (30)	(54,919)
Restricted stock grants and units delivered, net of cashless exercise (in shares)		107,892
Restricted stock grants and units delivered, net of cashless exercise	(306)	$ 1	(307)
Net income	85,377			85,377
Cash dividends declared on common stock	(30,892)			(30,892)
Other comprehensive income (loss)	(1,060)				(1,060)
Ending balance (in shares) at Dec. 31, 2015		74,988,210
Ending balance at Dec. 31, 2015	98,214	$ 750	9,718	95,328	(7,582)	0
Share-based compensation recognized	$ 6,408		6,408
Repurchase of common stock (in shares)	(2,500,000)	(2,504,427)
Repurchase of common stock	$ (39,946)	$ (25)	(15,594)	(24,327)
Restricted stock grants and units delivered, net of cashless exercise (in shares)		142,856
Restricted stock grants and units delivered, net of cashless exercise	(470)	$ 1	(471)
Stock options exercised, net of cashless exercise (in shares)		8,393
Stock options exercised, net of cashless exercise	(79)	$ 0	(79)
Net income	75,126			75,036		90
Cash dividends declared on common stock	(29,696)			(29,696)
Non-controlling interest on acquisition	3,409					3,409
Dividend reversal for forfeited options	18		18
Other comprehensive income (loss)	$ (4,809)				(4,809)
Ending balance (in shares) at Dec. 31, 2016	72,635,032	72,635,032
Ending balance at Dec. 31, 2016	$ 108,175	$ 726	0	116,341	(12,391)	3,499
Cumulative adjustment from implementation of ASU 2016-09	4,203			4,203
Share-based compensation recognized	$ 9,642		9,642
Repurchase of common stock (in shares)	(500,000)	(465,240)
Repurchase of common stock	$ (7,671)	$ (5)	(2,702)	(4,964)
Restricted stock grants and units delivered, net of cashless exercise (in shares)		215,343
Restricted stock grants and units delivered, net of cashless exercise	(1,497)	$ 2	(1,499)
Stock options exercised, net of cashless exercise (in shares)		8,798
Stock options exercised, net of cashless exercise	(91)	$ 0	(91)
Net income	55,419			55,054		365
Cash dividends declared on common stock	(21,747)			(21,747)
Other comprehensive income (loss)	$ 1,543				1,543
Ending balance (in shares) at Dec. 31, 2017	72,393,933	72,393,933
Ending balance at Dec. 31, 2017	$ 147,976	$ 723	$ 5,350	$ 148,887	$ (10,848)	$ 3,864