Segment Information (Schedule of Segment Revenues before Reimbursements, Segment Total Revenues and Segment Operating Profit) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Total revenues before reimbursements	$ 196,567	$ 165,224	$ 382,696	$ 326,669
Total revenues	223,056	184,713	425,918	362,781
Total segment operating profit	59,655	53,447	112,051	99,401
General and administrative expenses	35,968	34,912	71,135	71,991
Depreciation expense	4,262	4,943	8,848	9,940
Amortization expense	1,393	1,665	2,765	3,417
Other operating costs, net		2,295	32	3,278
Long-term compensation expense attributable to client-service employees (including share-based compensation expense)	3,493	1,344	5,116	2,789
Operating income	14,539	8,288	24,155	7,986
Interest and other (income) expense, net	(68)	651	(307)	1,721
Income from continuing operations before income tax expense	14,607	7,637	24,462	6,265
Healthcare [Member]
Segment Reporting Information [Line Items]
Total revenues before reimbursements	127,431	91,594	246,434	181,743
Total revenues	136,502	100,250	263,071	198,962
Total segment operating profit	40,137	27,375	76,892	47,765
Energy [Member]
Segment Reporting Information [Line Items]
Total revenues before reimbursements	40,002	36,644	76,251	70,348
Total revenues	55,450	44,183	99,150	81,820
Total segment operating profit	13,135	12,685	23,545	23,413
Financial Services Advisory and Compliance [Member]
Segment Reporting Information [Line Items]
Total revenues before reimbursements	29,134	36,986	60,011	74,578
Total revenues	31,104	40,280	63,697	81,999
Total segment operating profit	$ 6,383	$ 13,387	$ 11,614	$ 28,223