Stockholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		0 Months Ended	1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Jan. 28, 2015	Jan. 31, 2015
Proceeds from offering, net of commissions and underwriting discounts	$ 129,571
Underwriting discounts, commissions and offering expenses		827
Follow-on Offering [Member]
Common stock issued			3,942,200	3,942,200
Common stock issued price per share			$ 35.00	$ 35.00
Shares issued related to the exercise of over allotment option by underwriters				504,200
Proceeds from offering, net of commissions and underwriting discounts			129,571	129,571
Underwriting discounts, commissions and offering expenses			$ 473	$ 473