Segment Information (Schedule of Segment Revenues before Reimbursements, Segment Total Revenues and Segment Operating Profit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total revenues before reimbursements	$ 939,639	$ 938,746	$ 833,808
Total revenues	1,032,327	1,034,480	919,486
Total segment operating profit	296,307	319,949	273,828
General and administrative expenses	166,922	168,954	147,462
Depreciation expense	28,826	27,742	23,612
Amortization expense	8,960	11,507	8,613
Other operating costs (benefit), net	4,220	1,872	(9,900)
Long-term compensation expense attributable to client-service employees (including share-based compensation expense)	11,254	13,138	11,914
Operating income	76,125	96,736	92,127
Interest and other expense, net	5,544	3,325	3,974
Income before income tax expense	70,581	93,411	88,153
Healthcare [Member]
Segment Reporting Information [Line Items]
Total revenues before reimbursements	370,266	354,268	288,798
Total revenues	404,120	389,233	313,884
Total segment operating profit	111,188	115,163	90,869
Energy [Member]
Segment Reporting Information [Line Items]
Total revenues before reimbursements	124,492	115,940	106,023
Total revenues	146,425	133,612	124,491
Total segment operating profit	33,783	32,637	31,380
Financial Services Advisory and Compliance [Member]
Segment Reporting Information [Line Items]
Total revenues before reimbursements	140,336	152,166	124,359
Total revenues	159,410	173,391	142,959
Total segment operating profit	53,772	63,464	49,130
Disputes, Forensics and Legal Technology [Member]
Segment Reporting Information [Line Items]
Total revenues before reimbursements	304,545	316,372	314,628
Total revenues	322,372	338,244	338,152
Total segment operating profit	$ 97,564	$ 108,685	$ 102,449