Net Income (Loss) Per Share - Narrative (Detail) - $ / shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Share of common stock excluded from diluted net loss per share calculation	1.1	1.7	1.1	0.8
Shares of common stock at prices ranging, lower limit	$ 7.14	$ 3.93	$ 7.14	$ 7.41
Shares of common stock at prices ranging, upper limit	$ 19.95	$ 18.80	$ 19.95	$ 18.78
Deferred stock units, performance-based stock units and restricted stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Share of common stock excluded from diluted net loss per share calculation	0.4		0.4	0.3
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	3.0	3.0	3.0	3.0