Background and Basis of Presentation - Summary of EPS, Weighted Average Common Shares and Potential Common Shares Outstanding (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Numerator:
Net loss	$ (139.9)	$ (97.6)
Dividends on Series A convertible preferred stock	14.5	14.3
Net loss attributable to common stockholders	$ (154.4)	$ (111.9)
Denominator:
Weighted average common shares outstanding - basic	205.4	201.7
Weighted average common shares outstanding - diluted	205.4	201.7
Loss per share:
Basic	$ (0.75)	$ (0.55)
Diluted	$ (0.75)	$ (0.55)