Shareholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended			76 Months Ended	0 Months Ended
	Dec. 31, 2014 Vote	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Jan. 20, 2015	Feb. 13, 2002	Aug. 28, 2008	Jan. 31, 2015
Stockholders Equity Note [Line Items]
Common stock votes per share	1			1
Preferred stock, shares authorized	5,000	5,000		5,000
Shareholder rights plan, expiration period	2012-02
Repurchased and retired, aggregate price	$ 5,176	$ 5,834	$ 5,727
Series A Preferred Stock
Stockholders Equity Note [Line Items]
Preferred stock, shares authorized						2,000
Stock Repurchase Program
Stockholders Equity Note [Line Items]
Repurchased and retired, shares	47,424	75,000	60,000	2,000,000
Repurchased and retired, aggregate price	$ 5,175	$ 5,833	$ 5,727	$ 89,309
Stock Repurchase Program | Maximum
Stockholders Equity Note [Line Items]
Board of Directors authorized the repurchase of common stock							2,000,000
Subsequent Event
Stockholders Equity Note [Line Items]
Board of Directors authorized the repurchase of common stock								2,000,000
Subsequent Event | Dividend Declared
Stockholders Equity Note [Line Items]
Dividends declared per common share					$ 0.33
Cash dividend, date dividend paid					Feb. 16, 2015
Cash dividend, record date					Feb. 02, 2015