Indebtedness - Summary of Indebtedness at Estimated Fair Value (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Mortgage Loans Payable, Net		$ 228,554	$ 304,508
Senior Unsecured Notes, Net		567,889	546,607
Unsecured Term Loans		461,210	461,317
Unsecured Credit Facility		102,126	0
Total		1,359,779	1,312,432
Carrying Amount (A)
Debt Instrument [Line Items]
Mortgage Loans Payable, Net	[1]	223,804	297,716
Senior Unsecured Notes, Net	[1]	548,495	548,494
Unsecured Term Loans	[1]	460,000	460,000
Unsecured Credit Facility	[1]	102,000	0
Total	[1]	$ 1,334,299	$ 1,306,210

[1] The carrying amounts include unamortized premiums and discounts and exclude unamortized debt issuance costs.