Debt Issuance Costs (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Debt Issuance Costs
Capitalized debt issuance costs	$ 0	$ 2,658,000	$ 0
Unamortized debt issuance costs written off	(312,000)	(158,000)	(1,050,000)
Amortization of debt issuance costs	4,100,000	1,800,000	1,300,000
Debt issuance costs	11,915,000	12,204,000
Accumulated amortization	(11,915,000)	(7,831,000)
Debt issuance costs, net		$ 4,373,000