Net Income (Loss) Per Share - Narrative (Detail) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares of common stock at prices ranging, lower limit	$ 10.37	$ 9.83
Shares of common stock at prices ranging, upper limit	$ 18.45	$ 19.95
Employee stock options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Share of common stock excluded from diluted net loss per share calculation (in shares)	0.2	0.4
Restricted Stock Unit And Performance Stock Unit And Deferred Stock Unit [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Share of common stock excluded from diluted net loss per share calculation (in shares)	0.3	0.8
Convertible Senior Debentures due 2018 [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Share of common stock excluded from diluted net loss per share calculation (in shares)		0.8