Subsequent Events - Additional Information (Detail) (USD $)	1 Months Ended
	May 31, 2013	Oct. 31, 2013 Subsequent Event	Oct. 31, 2013 Follow-on offering Subsequent Event
Subsequent Event [Line Items]
Common stock initial public offering	9,686,171	1,908,803	6,366,513
Common stock issued per share		$ 23.75
Number of days granted for purchase of additional shares		30 days
Purchase of additional shares by underwriters		954,976
Underwriting discounts and commissions	$ 9,400,000	$ 6,400,000
Proceeds from public offering before offering costs		99,500,000
Offering expenses	5,200,000	800,000
Proceeds from public offering, net of underwriters discount		$ 98,700,000