Basic and Diluted Net Loss Per Share (Parenthetical) (Detail) - $ / shares shares in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	9.6	9.2	9.6	9.2
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

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details