Financial Instruments and Fair Values - Schedule of the Aggregate Carrying Value of Debt and Estimates of Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements liability	$ 31,227	$ 1,922
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements liability	31,227	1,922
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements liability	31,227	1,922
Mortgages | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	763,457	747,661
Mortgages | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	770,827	752,350
Senior Notes | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	348,888	348,810
Senior Notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	364,574	344,501
Secured Revolving Credit Facility | Mortgages | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	240,658	238,208
Secured Revolving Credit Facility | Mortgages | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	290,325	251,391
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 | Mortgages | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	0
Fair Value, Inputs, Level 1 | Senior Notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	0
Fair Value, Inputs, Level 1 | Secured Revolving Credit Facility | Mortgages | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	290,325	0
Fair Value, Inputs, Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap agreements liability	31,227	1,922
Fair Value, Inputs, Level 2 | Mortgages | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	0
Fair Value, Inputs, Level 2 | Senior Notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	0
Fair Value, Inputs, Level 2 | Secured Revolving Credit Facility | Mortgages | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	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 | Mortgages | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	770,827	752,350
Fair Value, Inputs, Level 3 | Senior Notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	364,574	344,501
Fair Value, Inputs, Level 3 | Secured Revolving Credit Facility | Mortgages | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	251,391
Revolving Credit Facility | Term Loan | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	262,830	262,545
Revolving Credit Facility | Term Loan | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	265,000	265,000
Revolving Credit Facility | Unsecured Revolving Credit Facility | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	35,192
Revolving Credit Facility | Unsecured Revolving Credit Facility | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	40,000
Revolving Credit Facility | Fair Value, Inputs, Level 1 | Term Loan | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	0
Revolving Credit Facility | Fair Value, Inputs, Level 1 | Unsecured Revolving Credit Facility | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	0
Revolving Credit Facility | Fair Value, Inputs, Level 2 | Term Loan | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	0
Revolving Credit Facility | Fair Value, Inputs, Level 2 | Unsecured Revolving Credit Facility | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	0	0
Revolving Credit Facility | Fair Value, Inputs, Level 3 | Term Loan | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	265,000	265,000
Revolving Credit Facility | Fair Value, Inputs, Level 3 | Unsecured Revolving Credit Facility | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair values of financial instruments	$ 0	$ 40,000