Net Income (Loss) Per Share - Narrative (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares of common stock at prices ranging, lower limit	$ 7.14	$ 3.93	$ 3.93
Shares of common stock at prices ranging, upper limit	$ 19.95	$ 18.80	$ 18.80
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	1.3	1.8	3.3
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	0.5	0.3	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