Basis of Presentation and Significant Accounting Policies - Additional Information (Details) $ in Thousands		3 Months Ended
	Apr. 17, 2018 center personnel	Mar. 31, 2018 USD ($) component segment	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Basis Of Presentation And Significant Accounting Policies [Line Items]
Number of reportable segments | segment		3
Number of components supplied to worldwide (more than) | component		1,300
Accumulated other comprehensive income		$ (4,435)		$ (9,454)
Retained earnings		1,053,090		990,652
Total inventories		10,600		8,600
Restricted cash and cash equivalents reclassified into other assets		8,000
Restricted cash and cash equivalents		$ 5,362		7,105
Effective tax rate		21.90%	30.60%
Effective income tax rate reconciliation, share-based compensation cost (benefit) amount		$ (2,200)	$ (2,300)
Gross unrecognized tax benefits		1,700
Increase in cash and cash equivalents and restricted cash and cash equivalents		151,336	104,713	213,144	$ 134,600
Accounting Standards Update 2016-01
Basis Of Presentation And Significant Accounting Policies [Line Items]
Accumulated other comprehensive income				2,200
Retained earnings				2,200
Accounting Standards Update 2016-18
Basis Of Presentation And Significant Accounting Policies [Line Items]
Increase in cash and cash equivalents and restricted cash and cash equivalents			8,800	$ 9,000
Cash Held for Future Decommissioning of Facilities
Basis Of Presentation And Significant Accounting Policies [Line Items]
Restricted cash and cash equivalents		2,600
Cash Held to Meet Reinsurance Reserve Requirements
Basis Of Presentation And Significant Accounting Policies [Line Items]
Restricted cash and cash equivalents		$ 5,400
Unsuccessful Outcome of Framework Agreement
Basis Of Presentation And Significant Accounting Policies [Line Items]
Loss contingency as a result of the Framework Agreement			30,000
Operating Income | Pro Forma | Accounting Standards Update 2017-07
Basis Of Presentation And Significant Accounting Policies [Line Items]
Net periodic benefit (income) cost			(6,900)
Other Nonoperating Income (Expense) | Pro Forma | Accounting Standards Update 2017-07
Basis Of Presentation And Significant Accounting Policies [Line Items]
Net periodic benefit (income) cost			$ 6,900
Canada Revenue Agency
Basis Of Presentation And Significant Accounting Policies [Line Items]
Statutory tax rate for Canada operations		25.00%
Subsequent Event | Sotera Health LLC's Nordion Medical Isotope Business
Basis Of Presentation And Significant Accounting Policies [Line Items]
Number of personnel acquired | personnel	150
Number of businesses acquired | center	2