Balance Sheet Accounts - Schedule of Other Current Assets, net (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred costs recoverable from the U.S. government	$ 45.7	$ 47.1
Income taxes receivable	23.7	43.4
Inventories	15.8	24.0
Prepaid expenses	15.2	13.9
Other	13.8	17.4
Other current assets, net	$ 114.2	$ 145.8