CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Loss (Income)	Retained Earnings (Deficit)	Noncontrolling Interests
Balance, Stockholders Equity at Dec. 31, 2015	$ 410,436	$ 35	$ 504,290	$ (26,966)	$ 15	$ (67,806)	$ 868
Balance (in shares) at Dec. 31, 2015		34,786,966
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock - employee stock purchase plan	2,483		2,483
Issuance of stock - employee stock purchase plan (shares)		63,688
Issuance of stock - 401 (k) plan	6,682		6,682
Issuance of stock - 401 (k) plan (shares)		145,660
Issuance/(cancellation) of non-vested stock	0
Issuance/(cancellation) of non-vested stock (shares)		257,263
Non-cash compensation	16,401		16,401
Tax benefit from stock options exercised and restricted stock vesting	7,241		7,241
Surrendered shares	(7,493)			(7,493)
Shares repurchased	(12,315)			(12,315)
Noncontrolling interest distribution	(329)						(329)
Assets contributed to equity investment	405		375				30
Net income	37,631					37,261	370
Balance, Stockholders Equity at Dec. 31, 2016	461,142	$ 35	537,472	(46,774)	15	(30,545)	939
Balance (in shares) at Dec. 31, 2016		35,253,577
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock - employee stock purchase plan	2,382		2,382
Issuance of stock - employee stock purchase plan (shares)		53,848
Issuance of stock - 401 (k) plan	8,223		8,223
Issuance of stock - 401 (k) plan (shares)		156,487
Issuance/(cancellation) of non-vested stock	0
Issuance/(cancellation) of non-vested stock (shares)		139,016
Exercise of stock options	4,554		4,554
Exercise of stock options (in shares)		144,206
Non-cash compensation	16,295		16,295
Tax benefit from stock options exercised and restricted stock vesting	448		0			448
Surrendered shares	(6,939)			(6,939)
Noncontrolling interest distribution	(216)						(216)
Assets contributed to equity investment	(146)		(146)				0
Net income	30,683					30,301	382
Balance, Stockholders Equity at Dec. 31, 2017	516,426	$ 35	568,780	(53,713)	15	204	1,105
Balance (in shares) at Dec. 31, 2017		35,747,134
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock - employee stock purchase plan	2,429		2,429
Issuance of stock - employee stock purchase plan (shares)		38,961
Issuance of stock - 401 (k) plan	9,232		9,232
Issuance of stock - 401 (k) plan (shares)		129,451
Issuance/(cancellation) of non-vested stock	0	$ 1	(1)
Issuance/(cancellation) of non-vested stock (shares)		174,044
Exercise of stock options	$ 5,953		5,953
Exercise of stock options (in shares)	162,690	162,690
Non-cash compensation	$ 17,887		17,887
Surrendered shares	(6,570)			(6,570)
Shares repurchased	(181,402)			(181,402)
Noncontrolling interest distribution	(1,090)						(1,090)
Repurchase of noncontrolling interest	(361)		(614)				253
Net income	120,129					119,346	783
Balance, Stockholders Equity at Dec. 31, 2018	$ 482,633	$ 36	$ 603,666	$ (241,685)	$ 15	$ 119,550	$ 1,051
Balance (in shares) at Dec. 31, 2018		36,252,280