Summary of Potentially Dilutive Common Stock Equivalents (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Average unamortized share-based compensation expense:
Exercise prices on common stock options, lower range	$ 3	$ 3	$ 3
Exercise prices on common stock options, upper range	10	10	10
Warrants
Average unamortized share-based compensation expense:
Weighted average exercise price of the Warrants	$ 5.73	$ 6.66	$ 6.68
Unvested Restricted Common Stock Awards
Average unamortized share-based compensation expense:
Potentially dilutive common stock, value	$ 1.3	$ 0.6	$ 0.7
Unvested Common Stock Options
Average unamortized share-based compensation expense:
Potentially dilutive common stock, value		$ 0.1	$ 0.7
Unvested Performance Share Awards
Average unamortized share-based compensation expense:
Potentially dilutive common stock, value	$ 1.0