Fair Value of Assets and Liabilities - Schedule of Fair Value and Carrying Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Carrying Amount
Fair value of financial instruments
Senior unsecured debt and mortgage notes payable	$ 681,675	$ 856,940
Fair Value
Fair value of financial instruments
Senior unsecured debt and mortgage notes payable	$ 693,328	$ 874,280

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant