Share-Based Incentives - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended
	Jan. 31, 2013	Oct. 31, 2012	Mar. 31, 2011
Restricted Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted	$ 2.2	$ 1.3
Period of restricted common stock award	3 years	3 years	5 years
Stock option granted			37,000
Fair value of fully vested common stock			0.4
Percentage of vest in common stock			20.00%
Unrestricted Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option granted			51,000
Fair value of fully vested common stock			$ 0.6