Subsequent Events (Details) (USD $) In Thousands, except Share data, unless otherwise specified			0 Months Ended		1 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Apr. 25, 2013 Underwritten Public Offering [Member] Common Stock [Member] Subsequent Event [Member]	Apr. 03, 2013 Underwritten Public Offering [Member] Common Stock [Member] Subsequent Event [Member]	Apr. 29, 2013 Underwritten Public Offering [Member] Common Stock [Member] Subsequent Event [Member]
Subsequent Event [Line Items]
Common shares issued				1,321,000
Common stock, par value	$ 0.521	$ 0.521		$ 0.521
Public offering price per share				$ 26.50
Share price to underwriters				$ 25.44
Length of option period to purchase overallotment of shares				30 days
Shares included in overallotment option				198,150
Shares issued upon exercise of overallotment option			100,000
Proceeds from issuance of common shares					$ 36,150