Equity Securities and Stock-Based Compensation (Details) (USD $) Share data in Millions, unless otherwise specified	1 Months Ended	3 Months Ended
	Feb. 29, 2012	Dec. 31, 2012	Dec. 31, 2011
Equity Securities and Stock-Based Compensation
Common stock, shares issued		11.5
Gross proceeds from issuance of common stock		$ 83,400,000
Offering costs		5,552,000
Net proceeds from issuance of common stock		77,823,000	0
Amount available for future offerings of securities	210,000,000	126,600,000
Treasury stock and related deferred compensation obligation at fair value		300,000
Carrying value of treasury stock and related deferred compensation obligation at cost		100,000
Stock-based awards to officers and employees (in shares)		0.5
Awards granted vesting period		3 years
Stock-based compensation		384,000	624,000
Total compensation cost related to unvested awards not yet recognized		$ 2,600,000