CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue, net (includes $4.6 million and $5.1 million with related parties for the three months ended September 30, 2019 and 2018, respectively, and $13.7 million and $9.2 million with related parties for the nine months ended September 30, 2019 and 2018, respectively)	$ 216,238	$ 179,253	$ 631,083	$ 512,474
Operating expenses:
Direct service costs, excluding depreciation and amortization	81,086	62,520	235,522	184,339
Reimbursed out-of-pocket expenses	70,984	61,476	212,563	173,587
Total direct costs	152,070	123,996	448,085	357,926
Selling, general and administrative	29,120	18,606	73,984	55,112
Depreciation	2,062	2,343	6,035	6,883
Amortization	2,995	7,390	11,834	22,171
Total operating expenses	186,247	152,335	539,938	442,092
Income from operations	29,991	26,918	91,145	70,382
Other expense, net:
Miscellaneous (expense) income, net	(273)	482	(574)	807
Interest expense, net	(253)	(1,941)	(1,956)	(6,558)
Total other expense, net	(526)	(1,459)	(2,530)	(5,751)
Income before income taxes	29,465	25,459	88,615	64,631
Income tax provision	5,488	6,154	17,985	14,207
Net income	$ 23,977	$ 19,305	$ 70,630	$ 50,424
Net income per share attributable to common shareholders:
Basic	$ 0.67	$ 0.54	$ 1.97	$ 1.41
Diluted	$ 0.63	$ 0.52	$ 1.88	$ 1.36
Weighted average common shares outstanding:
Basic	35,939	35,569	35,829	35,525
Diluted	37,835	37,125	37,507	36,795