CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Statement - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income	Retained Earnings	Noncontrolling Interests
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
Issuance of stock - employee stock purchase plan	1,787		1,787
Issuance of stock - employee stock purchase plan (shares)		32,909
Issuance of stock - 401(k) plan	7,185		7,185
Issuance of stock - 401(k) plan (shares)		113,082
Issuance/(cancellation) of non-vested stock	0	$ 1	(1)
Issuance/(cancellation) of non-vested stock (shares)		169,811
Exercise of stock options	2,749		2,749
Exercise of stock options (in shares)		83,713
Non-cash compensation	12,653		12,653
Surrendered Shares	(5,421)			(5,421)
Shares repurchased	(181,402)			(181,402)
Noncontrolling interest distribution	(530)						(530)
Repurchase of noncontrolling interest	(361)		(614)				(253)
Net income	92,409					91,885	524
Balance, Stockholders Equity at Sep. 30, 2018	445,495	$ 36	592,539	(240,536)	15	92,089	1,352
Balance (in shares) at Sep. 30, 2018		36,146,649
Balance, Stockholders Equity at Jun. 30, 2018	409,061	$ 36	585,137	(237,947)	15	60,712	1,108
Balance (in shares) at Jun. 30, 2018		36,044,177
Issuance of stock - employee stock purchase plan	630		630
Issuance of stock - employee stock purchase plan (shares)		8,673
Issuance of stock - 401(k) plan	2,404		2,404
Issuance of stock - 401(k) plan (shares)		28,123
Issuance/(cancellation) of non-vested stock	0	$ 0	0
Issuance/(cancellation) of non-vested stock (shares)		63,098
Exercise of stock options	140		140
Exercise of stock options (in shares)		2,578
Non-cash compensation	4,842		4,842
Surrendered Shares	(2,589)			(2,589)
Noncontrolling interest distribution	(180)						(180)
Repurchase of noncontrolling interest	(361)		(614)				(253)
Net income	31,548					31,377	171
Balance, Stockholders Equity at Sep. 30, 2018	445,495	$ 36	592,539	(240,536)	15	92,089	1,352
Balance (in shares) at Sep. 30, 2018		36,146,649
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
Issuance of stock - employee stock purchase plan	2,384		2,384
Issuance of stock - employee stock purchase plan (shares)		23,267
Issuance of stock - 401(k) plan	6,966		6,966
Issuance of stock - 401(k) plan (shares)		57,783
Issuance/(cancellation) of non-vested stock	0	$ 1	(1)
Issuance/(cancellation) of non-vested stock (shares)		185,515
Exercise of stock options	3,388		3,388
Exercise of stock options (in shares)		80,428
Non-cash compensation	18,451		18,451
Surrendered Shares	(9,385)			(9,385)
Noncontrolling interest distribution	(910)						(910)
Net income	99,938					99,178	760
Balance, Stockholders Equity at Sep. 30, 2019	603,465	$ 37	634,854	(251,070)	15	218,728	901
Balance (in shares) at Sep. 30, 2019		36,599,273
Balance, Stockholders Equity at Jun. 30, 2019	562,942	$ 36	623,309	(246,175)	15	184,596	1,161
Balance (in shares) at Jun. 30, 2019		36,445,591
Issuance of stock - employee stock purchase plan	850		850
Issuance of stock - employee stock purchase plan (shares)		8,230
Issuance of stock - 401(k) plan	2,353		2,353
Issuance of stock - 401(k) plan (shares)		19,381
Issuance/(cancellation) of non-vested stock	0	$ 1	(1)
Issuance/(cancellation) of non-vested stock (shares)		88,334
Exercise of stock options	2,045		2,045
Exercise of stock options (in shares)		37,737
Non-cash compensation	6,298		6,298
Surrendered Shares	(4,895)			(4,895)
Noncontrolling interest distribution	(453)						(453)
Net income	34,325					34,132	193
Balance, Stockholders Equity at Sep. 30, 2019	$ 603,465	$ 37	$ 634,854	$ (251,070)	$ 15	$ 218,728	$ 901
Balance (in shares) at Sep. 30, 2019		36,599,273