Summary of Potentially Dilutive Common Stock Equivalents (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Average unamortized share-based compensation expense:
Exercise prices on common stock options, lower range	$ 3.00	$ 3.00	$ 3.00	$ 3.00
Exercise prices on common stock options, upper range	10.00	10.00	10.00	10.00
Weighted average exercise price of the Warrants	$ 5.64	$ 5.64	$ 5.64	$ 5.81
Unvested Restricted Common Stock Awards
Average unamortized share-based compensation expense:
Average unamortized share-based compensation expense	$ 3.0	$ 1.6	$ 2.6	$ 1.3
Unvested Performance Share Awards
Average unamortized share-based compensation expense:
Average unamortized share-based compensation expense	$ 2.1	$ 0.6	$ 2.0	$ 0.3