Schedule II (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	$ 1,421	$ 1,472	$ 1,905
Additions to allowance for doubtful accounts	2,003	2,546	2,565
Deductions to allowance for doubtful accounts	(1,780)	(2,597)	(2,998)
Allowance for doubtful accounts, ending balance	1,644	1,421	1,472
Allowance for Doubtful Accounts - Straight Line Rent [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	692	257	316
Additions to allowance for doubtful accounts	1,503	1,501	1,412
Deductions to allowance for doubtful accounts	(1,376)	(1,066)	(1,471)
Allowance for doubtful accounts, ending balance	819	692	257
Allowance for Doubtful Accounts - Accounts Receivable [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	624	928	1,314
Additions to allowance for doubtful accounts	500	1,045	1,141
Deductions to allowance for doubtful accounts	(371)	(1,349)	(1,527)
Allowance for doubtful accounts, ending balance	753	624	928
Allowance for Doubtful Accounts - Notes Receivable [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for doubtful accounts, beginning balance	105	287	275
Additions to allowance for doubtful accounts	0	0	12
Deductions to allowance for doubtful accounts	(33)	(182)	0
Allowance for doubtful accounts, ending balance	$ 72	$ 105	$ 287