Segment Information Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 217,857	$ 220,754	$ 440,476	$ 425,199
Healthcare
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	85,356	101,939	180,934	195,621
Business Advisory
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	70,470	62,277	135,375	121,083
Education [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	62,031	56,538	124,167	108,495
Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	217,441	218,062	438,827	420,221
Transferred over Time [Member] | Healthcare
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	84,941	99,606	179,400	191,248
Transferred over Time [Member] | Business Advisory
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	70,470	62,277	135,375	121,083
Transferred over Time [Member] | Education [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	62,030	56,179	124,052	107,890
Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	416	2,692	1,649	4,978
Transferred at Point in Time [Member] | Healthcare
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	415	2,333	1,534	4,373
Transferred at Point in Time [Member] | Business Advisory
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Transferred at Point in Time [Member] | Education [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	359	115	605
Full-time Billable Consultants [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	178,677	179,005	359,515	346,924
Full-time Billable Consultants [Member] | Healthcare
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	58,221	69,548	123,666	134,366
Full-time Billable Consultants [Member] | Business Advisory
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	67,269	60,054	129,226	117,148
Full-time Billable Consultants [Member] | Education [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	53,187	49,403	106,623	95,410
Full-time Equivalents [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	39,180	41,749	80,961	78,275
Full-time Equivalents [Member] | Healthcare
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	27,135	32,391	57,268	61,255
Full-time Equivalents [Member] | Business Advisory
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,201	2,223	6,149	3,935
Full-time Equivalents [Member] | Education [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	8,844	7,135	17,544	13,085
Fixed-price Contract [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	89,574	99,494	183,927	197,133
Fixed-price Contract [Member] | Healthcare
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	50,803	59,681	106,588	123,265
Fixed-price Contract [Member] | Business Advisory
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	27,374	26,688	52,767	48,360
Fixed-price Contract [Member] | Education [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	11,397	13,125	24,572	25,508
Time-and-materials Contract [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	98,861	87,155	194,894	170,585
Time-and-materials Contract [Member] | Healthcare
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	14,029	14,275	28,762	27,038
Time-and-materials Contract [Member] | Business Advisory
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	40,264	33,804	77,853	69,113
Time-and-materials Contract [Member] | Education [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	44,568	39,076	88,279	74,434
Performance-based [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	16,761	22,553	36,328	35,027
Performance-based [Member] | Healthcare
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	14,480	22,021	33,401	33,831
Performance-based [Member] | Business Advisory
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,586	532	2,232	1,196
Performance-based [Member] | Education [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	695	0	695	0
Software Service, Support and Maintenance Arrangement [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	12,661	11,552	25,327	22,454
Software Service, Support and Maintenance Arrangement [Member] | Healthcare
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6,044	5,962	12,183	11,487
Software Service, Support and Maintenance Arrangement [Member] | Business Advisory
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,246	1,253	2,523	2,414
Software Service, Support and Maintenance Arrangement [Member] | Education [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 5,371	$ 4,337	$ 10,621	$ 8,553