Significant Accounting Policies - Trade Receivables, Net (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	$ 194.5	$ 184.3
Allowance for credit losses	(2.7)	(2.1)	$ (1.3)	$ (1.3)
Trade receivables, net	191.8	182.2
Trade receivables - billed
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	147.4	136.4
Trade receivables - unbilled
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	$ 47.1	$ 47.9