Common Stock Offering - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended		9 Months Ended
	Aug. 16, 2013	Jul. 25, 2013	Sep. 30, 2013	Sep. 30, 2012
Equity [Abstract]
Shares of common stock issued		4,500,000
Common stock issued, price per share		$ 18.00
Additional shares of common stock purchased by underwriters	675,000
Common stock exercise period for underwriters		30 days
Net proceeds from issuance of common stock		$ 88,043	$ 88,043	$ 56,565
Additional options granted to underwriters to cover over-allotments		675,000