Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	$ 378,089	$ 367,466	$ 1,122,491	$ 1,048,750
Revenues before reimbursable expenses	370,049	358,178	1,097,664	1,022,832
Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	219,281	221,111	649,757	605,486
Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	158,808	146,355	472,734	443,264
Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	214,517	214,688	634,415	589,137
Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	155,532	143,490	463,249	433,695
Healthcare
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	187,692	184,974	568,341	517,124
Revenues before reimbursable expenses	183,136	179,177	553,976	501,994
Healthcare \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	132,537	135,309	398,352	368,896
Healthcare \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	55,155	49,665	169,989	148,228
Healthcare \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	128,966	130,548	387,164	357,228
Healthcare \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	54,170	48,629	166,812	144,766
Education
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	123,253	113,432	361,985	332,865
Revenues before reimbursable expenses	121,048	111,043	355,384	325,884
Education \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	62,146	57,028	183,219	165,632
Education \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	61,107	56,404	178,766	167,233
Education \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	61,222	55,837	180,162	162,490
Education \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	59,826	55,206	175,222	163,394
Commercial:
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	67,144	69,060	192,165	198,761
Revenues before reimbursable expenses	65,865	67,958	188,304	194,954
Commercial: \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	24,598	28,774	68,186	70,958
Commercial: \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	42,546	40,286	123,979	127,803
Commercial: \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	24,329	28,303	67,089	69,419
Commercial: \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	$ 41,536	$ 39,655	$ 121,215	$ 125,535