Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	$ 441,284	$ 378,089	$ 1,257,180	$ 1,122,491
Revenues before reimbursable expenses	432,361	370,049	1,230,556	1,097,664
Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	261,962	219,281	725,469	649,757
Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	179,322	158,808	531,711	472,734
Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	256,319	214,517	709,362	634,415
Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	176,042	155,532	521,194	463,249
Education
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	131,874	123,253	388,576	361,985
Revenues before reimbursable expenses	129,424	121,048	381,473	355,384
Education \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	67,911	62,146	200,920	183,219
Education \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	63,963	61,107	187,656	178,766
Education \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	66,458	61,222	197,331	180,162
Education \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	62,966	59,826	184,142	175,222
Commercial:
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	85,058	67,144	237,660	192,165
Revenues before reimbursable expenses	83,396	65,865	233,230	188,304
Commercial: \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	25,745	24,598	59,062	68,186
Commercial: \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	59,313	42,546	178,598	123,979
Commercial: \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	25,494	24,329	58,535	67,089
Commercial: \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	57,902	41,536	174,695	121,215
Healthcare
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	224,352	187,692	630,944	568,341
Revenues before reimbursable expenses	219,541	183,136	615,853	553,976
Healthcare \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	168,306	132,537	465,487	398,352
Healthcare \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	56,046	55,155	165,457	169,989
Healthcare \| Consulting And Managed Services Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	164,367	128,966	453,496	387,164
Healthcare \| Digital Capability [Member]
Disaggregation of Revenue [Line Items]
Revenues before reimbursable expenses	$ 55,174	$ 54,170	$ 162,357	$ 166,812