Business Combinations, Acquisitions, and Business Disposals - Schedule of Fair Value of Net Assets Acquired (Details) - USD ($) $ in Millions			12 Months Ended
	Dec. 01, 2025	Jul. 31, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Business Combination [Line Items]
Goodwill			$ 1,872.4	$ 1,426.2	$ 1,447.6
GAAP purchase consideration, net of cash acquired			661.9	1.0	31.4
Nuclear & Safety
Business Combination [Line Items]
Goodwill			$ 1,238.4	$ 792.2	$ 814.2
Certrec
Business Combination [Line Items]
Purchase consideration		$ 82.9
GAAP purchase consideration, net of cash acquired		80.6
Certrec | Leasehold Improvements
Business Combination [Line Items]
Useful life			2 years 8 months 12 days
Certrec | Developed technology | Minimum
Business Combination [Line Items]
Useful life			5 years
Certrec | Developed technology | Maximum
Business Combination [Line Items]
Useful life			15 years
Certrec | Customer relationships
Business Combination [Line Items]
Useful life			10 years
Certrec | Trade names
Business Combination [Line Items]
Useful life			10 years
Certrec | Backlog
Business Combination [Line Items]
Useful life			3 years
Certrec | Nuclear & Safety
Business Combination [Line Items]
Goodwill		55.7
Total amortizable intangible assets		29.9
Cash		2.3
Restricted cash—current		0.0
Accounts receivable, net		0.7
Costs in excess of billings		0.0
Inventories		0.0
Prepaid expenses and other currents assets		0.1
Property, plant, and equipment, net		0.0
Other assets		0.8
Accounts payable		(0.3)
Deferred contract revenue		(4.2)
Accrued expenses and other current liabilities		(1.6)
Deferred income taxes, non-current		0.0
Other liabilities, non-current		(0.5)
Net tangible assets acquired		(2.7)
Purchase consideration		82.9
Less: cash and restricted cash acquired		2.3
GAAP purchase consideration, net of cash acquired		80.6
Acquiree revenue post acquisition through the period ended December 31, 2025		6.1
Acquiree loss from operations post acquisition through the period ended December 31, 2025		(0.4)
Certrec | Nuclear & Safety | Leasehold Improvements
Business Combination [Line Items]
Total amortizable intangible assets		0.0
Certrec | Nuclear & Safety | Developed technology
Business Combination [Line Items]
Total amortizable intangible assets		19.9
Certrec | Nuclear & Safety | Customer relationships
Business Combination [Line Items]
Total amortizable intangible assets		8.6
Certrec | Nuclear & Safety | Trade names
Business Combination [Line Items]
Total amortizable intangible assets		1.4
Certrec | Nuclear & Safety | Backlog
Business Combination [Line Items]
Total amortizable intangible assets		$ 0.0
Paragon
Business Combination [Line Items]
Purchase consideration	$ 588.4
GAAP purchase consideration, net of cash acquired	581.3
Paragon | Leasehold Improvements
Business Combination [Line Items]
Useful life			2 years 8 months 12 days
Paragon | Developed technology | Minimum
Business Combination [Line Items]
Useful life			5 years
Paragon | Developed technology | Maximum
Business Combination [Line Items]
Useful life			15 years
Paragon | Customer relationships
Business Combination [Line Items]
Useful life			10 years
Paragon | Trade names
Business Combination [Line Items]
Useful life			10 years
Paragon | Backlog
Business Combination [Line Items]
Useful life			3 years
Paragon | Nuclear & Safety
Business Combination [Line Items]
Goodwill	343.7
Total amortizable intangible assets	250.5
Cash	4.6
Restricted cash—current	2.5
Accounts receivable, net	14.3
Costs in excess of billings	12.4
Inventories	16.3
Prepaid expenses and other currents assets	2.3
Property, plant, and equipment, net	1.4
Other assets	2.3
Accounts payable	(6.9)
Deferred contract revenue	(11.0)
Accrued expenses and other current liabilities	(9.9)
Deferred income taxes, non-current	(32.9)
Other liabilities, non-current	(1.2)
Net tangible assets acquired	(5.8)
Purchase consideration	588.4
Less: cash and restricted cash acquired	7.1
GAAP purchase consideration, net of cash acquired	581.3
Acquiree revenue post acquisition through the period ended December 31, 2025	9.0
Acquiree loss from operations post acquisition through the period ended December 31, 2025	(1.8)
Paragon | Nuclear & Safety | Leasehold Improvements
Business Combination [Line Items]
Total amortizable intangible assets	2.0
Paragon | Nuclear & Safety | Developed technology
Business Combination [Line Items]
Total amortizable intangible assets	52.1
Paragon | Nuclear & Safety | Customer relationships
Business Combination [Line Items]
Total amortizable intangible assets	171.3
Paragon | Nuclear & Safety | Trade names
Business Combination [Line Items]
Total amortizable intangible assets	12.6
Paragon | Nuclear & Safety | Backlog
Business Combination [Line Items]
Total amortizable intangible assets	$ 12.5