Organization - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2015 Segment
Organization And Nature Of Business [Line Items]
Number of operating segment		1
Follow on offering price per share	$ 40.00	$ 40.00
Proceeds from offering and over-allotment option, net	$ 108.4
Follow-on Offering
Organization And Nature Of Business [Line Items]
Stock issued during the period	2,870,000
Underwriting discounts, commissions and offering expenses, net	$ 0.4
Underwriters Overallotment Option
Organization And Nature Of Business [Line Items]
Stock issued during the period	374,348