Basis of Presentation and Summary of Significant Accounting Policies (Schedule of Material Difference between the Carrying Amounts and the Estimated Fair Values of Financial Instruments) (Details) (USD $)	Jun. 30, 2011	Dec. 31, 2010
Basis of Presentation and Summary of Significant Accounting Policies
Investment in direct financing lease, Carrying Amount	$ 11,513,000	$ 12,185,000
Investment in direct financing lease, Fair Value	13,441,000	14,439,000
Note receivable from APM, Carrying Amount	5,053,000	4,880,000
Note receivable from APM, Fair Value	8,113,000	7,970,000
Debt, Carrying Amount	(1,104,294,000)	(1,156,568,000)
Debt, Fair Value	(1,166,150,000)	(1,206,347,000)
Material differences between the carrying amounts and the estimated fair values, except items listed above	$ 0	$ 0