Financial Instruments and Fair Values - Schedule of the Aggregate Carrying Value of Debt and Estimates of Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements liability	$ 32,157	$ 1,922
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements liability	32,157	1,922
Carrying Amount | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	767,717	747,661
Carrying Amount | Mortgages | Floating Rate Debt - Secured Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	239,841	238,208
Carrying Amount | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	348,862	348,810
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements liability	32,157	1,922
Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	778,349	752,350
Fair Value | Mortgages | Floating Rate Debt - Secured Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	252,794	251,391
Fair Value | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	368,165	344,501
Fair Value, Inputs, Level 1 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements liability	0	0
Fair Value, Inputs, Level 1 | Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Fair Value, Inputs, Level 1 | Fair Value | Mortgages | Floating Rate Debt - Secured Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Fair Value, Inputs, Level 1 | Fair Value | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Fair Value, Inputs, Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements liability	32,157	1,922
Fair Value, Inputs, Level 2 | Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Fair Value, Inputs, Level 2 | Fair Value | Mortgages | Floating Rate Debt - Secured Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Fair Value, Inputs, Level 2 | Fair Value | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Fair Value, Inputs, Level 3 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements liability	0	0
Fair Value, Inputs, Level 3 | Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	778,349	752,350
Fair Value, Inputs, Level 3 | Fair Value | Mortgages | Floating Rate Debt - Secured Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	252,794	251,391
Fair Value, Inputs, Level 3 | Fair Value | Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	368,165	344,501
Revolving Credit Facility | Carrying Amount | Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	262,735	262,545
Revolving Credit Facility | Carrying Amount | Unsecured Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	40,000	35,192
Revolving Credit Facility | Fair Value | Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	265,000	265,000
Revolving Credit Facility | Fair Value | Unsecured Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	40,000	40,000
Revolving Credit Facility | Fair Value, Inputs, Level 1 | Fair Value | Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Revolving Credit Facility | Fair Value, Inputs, Level 1 | Fair Value | Unsecured Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Revolving Credit Facility | Fair Value, Inputs, Level 2 | Fair Value | Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Revolving Credit Facility | Fair Value, Inputs, Level 2 | Fair Value | Unsecured Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	0	0
Revolving Credit Facility | Fair Value, Inputs, Level 3 | Fair Value | Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	265,000	265,000
Revolving Credit Facility | Fair Value, Inputs, Level 3 | Fair Value | Unsecured Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 40,000	$ 40,000