Balance Sheet Accounts and Supplemental Disclosures - Accounts Receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Billed	$ 75.3	$ 122.9
Reserve on billed trade receivables	0.0	(10.6)
Other trade receivables	0.3	0.2
Accounts receivable, net	75.6	$ 112.5
Accounts receivable, allowance for credit loss, writeoff	$ 10.6