CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury	Additional Paid-In Capital	Retained Earnings	Noncontrolling Interest Non Redeemable
Beginning balance, Amount at Dec. 31, 2017	$ 506,591	$ 226	$ (42,249)	$ 126,490	$ 364,401	$ 57,723
Beginning balance (in shares) at Dec. 31, 2017		22,640,046
Beginning balance, Treasury (in shares) at Dec. 31, 2017			4,890,504
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,592				4,995	597
Acquired noncontrolling interest	1,235					1,235
Noncontrolling interest distributions	(615)					(615)
NCI acquired, net of sales	3,554			(2,029)		5,583
Purchase of additional controlling interest	(56)			(44)		(12)
Nonvested stock compensation	1,601			1,601
Restricted share grants		$ 2		(2)
Restricted stock vesting (in shares)		165,567
Treasury shares redeemed to pay income tax	(3,467)		$ (3,467)
Treasury shares redeemed to pay income tax (in shares)			56,772
Issuance of common stock under Employee Stock Purchase Plan	332			332
Issuance of common stock under Employee Stock Purchase Plan (in shares)		5,534
Ending balance, Amount at Mar. 31, 2018	514,767	$ 228	$ (45,716)	126,348	369,396	64,511
Ending balance (in shares) at Mar. 31, 2018		22,811,147
Ending balance, Treasury (in shares) at Mar. 31, 2018			4,947,276
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18,187				16,797	1,390
Acquired noncontrolling interest	35,239					35,239
Noncontrolling interest distributions	(504)					(504)
NCI acquired, net of sales	(591)			(591)		0
Nonvested stock compensation	2,318			2,318
Restricted stock vesting (in shares)		10,818
Treasury shares redeemed to pay income tax	(628)		$ (628)
Treasury shares redeemed to pay income tax (in shares)			6,389
Merger consideration	795,405	$ 127		795,278
Merger consideration (in shares)		12,765,288
Issuance of common stock under Employee Stock Purchase Plan	302			302
Issuance of common stock under Employee Stock Purchase Plan (in shares)		5,171
Ending balance, Amount at Jun. 30, 2018	1,364,495	$ 355	$ (46,344)	923,655	386,193	100,636
Ending balance (in shares) at Jun. 30, 2018		35,592,424
Ending balance, Treasury (in shares) at Jun. 30, 2018			4,953,665
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,551				21,230	1,321
Acquired noncontrolling interest	1,671					1,671
Noncontrolling interest distributions	(544)					(544)
Purchase of additional controlling interest	7,346			7,705		(359)
Nonvested stock compensation	3,417			3,417
Restricted stock vesting (in shares)		34,970
Treasury shares redeemed to pay income tax	(2,624)		$ (2,624)
Treasury shares redeemed to pay income tax (in shares)			4,758
Issuance of common stock under Employee Stock Purchase Plan	382	$ 1		381
Issuance of common stock under Employee Stock Purchase Plan (in shares)		4,682
Ending balance, Amount at Sep. 30, 2018	1,396,694	$ 356	$ (48,968)	935,158	407,423	102,725
Ending balance (in shares) at Sep. 30, 2018		35,632,076
Ending balance, Treasury (in shares) at Sep. 30, 2018			4,958,423
Beginning balance, Amount at Dec. 31, 2018	$ 1,424,474	$ 356	$ (49,374)	937,968	427,975	107,549
Beginning balance (in shares) at Dec. 31, 2018		35,636,414
Beginning balance, Treasury (in shares) at Dec. 31, 2018	4,958,721		4,958,721
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 20,542				18,856	1,686
Acquired noncontrolling interest	820					820
Noncontrolling interest distributions	(6,799)					(6,799)
NCI acquired, net of sales	(18,000)					(18,000)
Nonvested stock compensation	1,804			1,804
Restricted share grants	2	$ 2
Restricted stock vesting (in shares)		174,562
Treasury shares redeemed to pay income tax	(7,692)		$ (7,577)	(115)
Treasury shares redeemed to pay income tax (in shares)			85,509
Issuance of common stock under Employee Stock Purchase Plan	$ 478			478
Issuance of common stock under Employee Stock Purchase Plan (in shares)	5,357	5,357
Ending balance, Amount at Mar. 31, 2019	$ 1,415,629	$ 358	$ (56,951)	940,135	446,831	85,256
Ending balance (in shares) at Mar. 31, 2019		35,816,333
Ending balance, Treasury (in shares) at Mar. 31, 2019			5,044,230
Beginning balance, Amount at Dec. 31, 2018	$ 1,424,474	$ 356	$ (49,374)	937,968	427,975	107,549
Beginning balance (in shares) at Dec. 31, 2018		35,636,414
Beginning balance, Treasury (in shares) at Dec. 31, 2018	4,958,721		4,958,721
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares redeemed to pay income tax (in shares)	69,213
Ending balance, Amount at Sep. 30, 2019	$ 1,481,930	$ 359	$ (58,796)	945,575	501,898	92,894
Ending balance (in shares) at Sep. 30, 2019		35,857,938
Ending balance, Treasury (in shares) at Sep. 30, 2019	5,060,266		5,060,266
Beginning balance, Amount at Mar. 31, 2019	$ 1,415,629	$ 358	$ (56,951)	940,135	446,831	85,256
Beginning balance (in shares) at Mar. 31, 2019		35,816,333
Beginning balance, Treasury (in shares) at Mar. 31, 2019			5,044,230
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	26,897				25,000	1,897
Acquired noncontrolling interest	6,170					6,170
Noncontrolling interest distributions	(2,026)					(2,026)
NCI acquired, net of sales	(752)			(1,283)		531
Nonvested stock compensation	2,588			2,588
Restricted stock vesting (in shares)		17,145
Treasury shares redeemed to pay income tax	(912)		$ (942)	30
Treasury shares redeemed to pay income tax (in shares)			8,697
Issuance of common stock under Employee Stock Purchase Plan	$ 453			453
Issuance of common stock under Employee Stock Purchase Plan (in shares)	4,301	4,301
Ending balance, Amount at Jun. 30, 2019	$ 1,448,047	$ 358	$ (57,893)	941,923	471,831	91,828
Ending balance (in shares) at Jun. 30, 2019		35,837,779
Ending balance, Treasury (in shares) at Jun. 30, 2019			5,052,927
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31,546				30,067	1,479
Acquired noncontrolling interest	1,868					1,868
Noncontrolling interest distributions	(2,162)					(2,162)
NCI acquired, net of sales	700			819		(119)
Nonvested stock compensation	1,990			1,990
Restricted share grants	1	$ 1
Restricted stock vesting (in shares)		14,799
Treasury shares redeemed to pay income tax	(669)		$ (903)	234
Treasury shares redeemed to pay income tax (in shares)			7,339
Issuance of common stock under Employee Stock Purchase Plan	$ 609			609
Issuance of common stock under Employee Stock Purchase Plan (in shares)	5,360	5,360
Ending balance, Amount at Sep. 30, 2019	$ 1,481,930	$ 359	$ (58,796)	$ 945,575	$ 501,898	$ 92,894
Ending balance (in shares) at Sep. 30, 2019		35,857,938
Ending balance, Treasury (in shares) at Sep. 30, 2019	5,060,266		5,060,266