Indebtedness - Summary of Indebtedness at Estimated Fair Value (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Mortgage Loans Payable		$ 85,452	$ 148,770
Senior Unsecured Notes, Net		1,085,573	1,096,262
Unsecured Term Loans		460,647	458,207
Unsecured Credit Facility		74,000	0
Total		1,705,672	1,703,239
Carrying Amount (A)
Debt Instrument [Line Items]
Mortgage Loans Payable	[1]	83,117	144,214
Senior Unsecured Notes, Net	[1]	998,511	998,506
Unsecured Term Loans	[1]	460,000	460,000
Unsecured Credit Facility	[1]	74,000	0
Total	[1]	$ 1,615,628	$ 1,602,720

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