Stockholders' Equity (Narrative) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	May 18, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stockholders' Equity [Line Items]
Public offering, common stock	6,037,500
Common stock per share price	$ 10.70
Net proceeds from issuance of common stock	$ 62,803	$ 8,895	$ 71,053	$ 6,723
Common Stock Over-Allotment Option [Member]
Stockholders' Equity [Line Items]
Public offering, common stock	787,500