Stockholders' Equity - Additional Information (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	6 Months Ended
	Feb. 28, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Shelf Registration	Dec. 31, 2012 Shelf Registration Maximum
Class of Stock [Line Items]
Common stock issued	8.0			8.0
Common stock, offering price	$ 17.75
Proceeds from common stock issuance	$ 133,200,000	$ 136,515,000	$ 2,591,000
Aggregate initial offering price of common stock					$ 150,000,000