Accounts Receivable/Deferred Rent Receivable (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounts Receivable and Deferred Rent Receivable [Abstract]
Allowance for Doubtful Accounts Receivable	$ 7,000,000	$ 7,500,000
Provision for Doubtful Accounts	$ 540,000	$ (1,900,000)	$ 3,900,000