Leases - Tenant Accounts Receivable (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) leases	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Cash Basis Leases | leases			6
Accrued Rent Adjustment To Rental Income Resulting From Lease Collectibility Assessment	$ 1,200,000	$ 0	$ 900,000	$ 0
Contractual Rent Adjustment To Rental Income Resulting From Lease Collectibility Assessment	600,000	0	600,000	0
Lease Security Deposits Available in Letters of Credit	28,200,000		28,200,000		$ 22,600,000
Lease security deposits in restricted cash	700,000		700,000		700,000
Lease security deposits included in tenant prepaid rent and security deposits on the Balance Sheet	10,000,000.0		10,000,000.0		9,800,000
Real Estate Taxes, Tenant Responsibility	4,900,000	$ 4,100,000	9,700,000	$ 8,000,000.0
Accrued Income Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Deferred Rent Receivables, Net	$ 51,300,000		$ 51,300,000		$ 44,300,000