Net Income (Loss) Per Share of Common Stock - Schedule of Computation of Basic and Diluted Net Income (Loss) Per Share of Common Stock (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
BASIC AND DILUTED:
Net income (loss) attributable to common stockholders	$ (41.7)	$ 27.8	$ (23.0)	$ (122.2)	$ (150.3)	$ (103.9)	$ (36.9)	$ (376.4)
Weighted-average common shares outstanding	1,097.1			1,076.7			1,090.4	995.6
Net income (loss) per share attributable to common stockholders	$ (0.04)			$ (0.11)			$ (0.03)	$ (0.38)