Accumulated Other Comprehensive Income (Loss) - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ 9,189.5	$ 1,869.9	$ 1,676.0	$ 1,476.8
Other comprehensive loss, net of tax:	$ (1.4)	0.0	0.0
Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity		$ (1.0)	0.0	0.0
Cumulative Effect, Period of Adoption, Adjustment | Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity			(6.7)	$ 0.3
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2018-02
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity			$ (8.2)