Segment Reporting - Disaggregation of Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	$ 1,007.0	$ 1,020.6	$ 1,975.3	$ 1,988.9
Commercial
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	701.7	708.1	1,377.2	1,380.3
Commercial \| Consumer and Industrial Sector [Member]
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	230.8	235.1	454.8	449.3
Commercial \| Technology, Media, and Telecommunications Sector [Member]
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	144.7	137.0	282.9	270.2
Commercial \| Financial Services Sector [Member]
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	132.5	135.8	259.3	270.2
Commercial \| Healthcare Sector [Member]
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	116.9	118.0	233.0	225.4
Commercial \| Business Services Sector [Member]
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	76.8	82.2	147.2	165.2
Federal Government
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	305.3	312.5	598.1	608.6
Federal Government \| Firm-fixed-price
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	83.3	86.0	173.5	176.0
Federal Government \| T&M
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	115.6	128.1	221.6	254.2
Federal Government \| Cost reimbursable
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	106.4	98.4	203.0	178.4
Other Federal [Member] \| Federal Government
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	32.6	31.2	65.1	62.3
Department of Homeland Security [Member] \| Federal Government
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	94.2	87.3	178.8	161.4
Federal Civilian [Member] \| Federal Government
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	51.3	57.8	105.9	119.8
Department of Defense & Intelligence Agencies [Member] \| Federal Government
Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Product and Service, Revenue [Line Items]
Revenues	$ 127.2	$ 136.2	$ 248.3	$ 265.1