Debt - Schedule of Net Carrying Amount of Liability and Equity Components of Notes (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021	Dec. 17, 2020	Jun. 14, 2019
Liability component:
Principal	$ 1,564.5	$ 1,564.5
Unamortized transaction costs	(22.4)	(19.6)
Net carrying amount	1,542.1	1,343.8
Unamortized debt discount		(201.1)
Equity component, net of transaction costs		278.6
Convertible Senior Notes Due 2024 [Member]
Liability component:
Principal	690.0	690.0		$ 690.0
Unamortized transaction costs	(8.2)	(7.6)
Net carrying amount	681.8	621.9
Unamortized debt discount		(60.5)
Equity component, net of transaction costs		114.9		$ 118.0
Convertible Senior Notes Due 2026 [Member]
Liability component:
Principal	874.5	874.5	$ 874.5
Unamortized transaction costs	(14.2)	(12.0)
Net carrying amount	$ 860.3	721.9
Unamortized debt discount		(140.6)
Equity component, net of transaction costs		$ 163.7	$ 167.1