Basic and Diluted Net Loss Per Share (Parenthetical) (Detail) - $ / shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	10.0	9.7	10.0	9.7
2024 Convertible Notes [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Debt instrument, conversion price	$ 73.42		$ 73.42
Effect on diluted net earnings (loss) per share	$ 0		$ 0	$ 0