Number of Unvested Shares of Restricted Stock and Weighted Average Fair Value of Shares at Date of Grant (Parenthetical) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2014 Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares used to settle minimum employee withholding tax obligations	7,944
Number of employee that shares used to settle minimum employee withholding tax obligations	1
Value of shares used to settle minimum employee withholding tax obligations	$ 0.2
Shares of common stock delivered net	32,111