Shareholders' Equity (Details) (USD $)	0 Months Ended				12 Months Ended
	Nov. 02, 2012	Sep. 27, 2012	Dec. 08, 2009	Feb. 07, 2006	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Preferred stock
Preferred stock issued (in shares)				3,475,000	0	3,475,000
Preferred stock dividend rate (as a percent)				9.00%
Preferred stock liquidation preference (in dollars per share)				$ 10.00
Preferred stock liquidation preference				$ 34,800,000
Net proceeds from issuance of preferred stock				31,900,000
Preferred stock dividend	147,687			260,625
Preferred stock redemption costs					2,835,000
Preferred stock redemption amount	34,800,000
Preferred stock redemption price (in dollars per share)	$ 10.00
Common Stock Repurchase
Repurchase of common stock authorized by Board of Directors		100,000,000	100,000,000
Number of years for repurchase of common stock		5 years
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased (in shares)					928,261
Common stock repurchased, value					$ 12,736,000	$ 5,661,000	$ 4,156,000
Weighted average price per share (in dollars per share)					$ 13.72
Common shares outstanding					8,715,580	9,109,663