Schedule II (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	$ 3,013	$ 3,843	$ 4,903
Additions to allowance for doubtful accounts	2,619	1,516	2,335
Deductions to allowance for doubtful accounts	(3,443)	(2,346)	(3,395)
Allowance for doubtful accounts, ending balance	2,189	3,013	3,843
Allowance for Doubtful Accounts - Straight Line Rent [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	1,063	813	1,294
Additions to allowance for doubtful accounts	1,277	545	1,382
Deductions to allowance for doubtful accounts	(1,740)	(295)	(1,863)
Allowance for doubtful accounts, ending balance	600	1,063	813
Allowance for Doubtful Accounts - Accounts Receivable [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	1,648	2,848	3,548
Additions to allowance for doubtful accounts	1,342	851	767
Deductions to allowance for doubtful accounts	(1,676)	(2,051)	(1,467)
Allowance for doubtful accounts, ending balance	1,314	1,648	2,848
Allowance for Doubtful Accounts - Notes Receivable [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	302	182	61
Additions to allowance for doubtful accounts	0	120	186
Deductions to allowance for doubtful accounts	(27)	0	(65)
Allowance for doubtful accounts, ending balance	$ 275	$ 302	$ 182