Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement Of Partners Capital [Abstract]
Net income (loss)	$ 27.8	$ (150.3)	$ 4.8	$ (254.2)
Other comprehensive income (loss):
Change in foreign currency translation adjustment	11.0	16.3	(4.5)	(12.7)
Net change in unrealized gains (losses) on available-for-sale marketable debt securities, net of tax		1.4	(0.1)	0.4
Other comprehensive income (loss), net of tax	11.0	17.7	(4.6)	(12.3)
Comprehensive income (loss)	$ 38.8	$ (132.6)	$ 0.2	$ (266.5)