Schedule II (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	$ 4,903	$ 6,672	$ 5,951
Additions to allowance for doubtful accounts	2,335	2,522	4,009
Deductions to allowance for doubtful accounts	(3,279)	(4,291)	(3,288)
Allowance for doubtful accounts, ending balance	3,959	4,903	6,672
Allowance for Doubtful Accounts - Straight Line Rent [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	1,294	2,209	2,443
Additions to allowance for doubtful accounts	1,382	710	635
Deductions to allowance for doubtful accounts	(1,747)	(1,625)	(869)
Allowance for doubtful accounts, ending balance	929	1,294	2,209
Allowance for Doubtful Accounts - Accounts Receivable [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	3,548	3,595	2,810
Additions to allowance for doubtful accounts	767	1,616	2,961
Deductions to allowance for doubtful accounts	(1,467)	(1,663)	(2,176)
Allowance for doubtful accounts, ending balance	2,848	3,548	3,595
Allowance for Doubtful Accounts - Notes Receivable [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	61	868	698
Additions to allowance for doubtful accounts	186	196	413
Deductions to allowance for doubtful accounts	(65)	(1,003)	(243)
Allowance for doubtful accounts, ending balance	$ 182	$ 61	$ 868