Net Income (Loss) Per Share - Narrative (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 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	1.3	0.9
Shares of common stock at prices ranging, lower limit	$ 7.14	$ 7.41
Shares of common stock at prices ranging, upper limit	$ 19.95	$ 18.76
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	0.3
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