Summary of Significant Accounting Policies - Summary of Components Used to Calculate Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Significant Accounting Policies [Line Items]
Net income (loss) available to common shareholders	$ 10,858	$ 17,852	$ (7,202)
Weighted average number of common shares outstanding	23,816	23,446	21,969
Effect of dilutive restricted grants		63
Effect of dilutive options	41	29
Weighted average number of common shares outstanding used to calculate diluted earnings per share	23,857	23,538	21,969