Description of Business - Additional Information (Detail) (USD $)	1 Months Ended		9 Months Ended
	Feb. 28, 2014	Jan. 31, 2014	Sep. 30, 2014	Sep. 30, 2013
Subsidiary, Sale of Stock [Line Items]
Underwriters partially exercised an overallotment option, shares		2,972,972
Proceeds from underwritten public offering		$ 55,000,000
Underwriters partially exercised an overallotment option, additional gross proceeds	6,400,000		170,000	378,000
Proceeds from underwritten public offering after fees and commissions	$ 57,000,000
Over-Allotment Option [Member]
Subsidiary, Sale of Stock [Line Items]
Underwriters partially exercised an overallotment option, shares	345,945