Margin Account Loan (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	13 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Margin Account Loan [Abstract]
Line of credit facility initiation date	Jul. 26, 2011
Interest rate during period (percent)	2.50%	2.50%
Reduction in Wells Fargo base rate (percent)	2.75%
Margin account loan liability	$ 7,051	$ 7,051
Marketable securities – restricted	14,068	14,500
Increase in accrued interest	$ 130