Organization, Basis of Presentation and Summary of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Organization, Basis of Presentation and Summary of Significant Accounting Policies (Details) [Line Items]
Lease liability	$ 17,675,000
Payroll related costs capitalized		$ 1,300,000	$ 1,200,000
Taxable income minimum distribution portion not subject to federal taxation (in percentage)	90.00%
Real estate improvements	$ 38,000,000.0	40,300,000
Acquisition transaction costs	0	0	$ 4,000
Allowance for doubtful accounts receivable	$ 8,200,000	$ 6,900,000
Number of segments | segment	1
Minimum | Building
Organization, Basis of Presentation and Summary of Significant Accounting Policies (Details) [Line Items]
PPE useful life (in years)	39 years
Minimum | Building Improvements
Organization, Basis of Presentation and Summary of Significant Accounting Policies (Details) [Line Items]
PPE useful life (in years)	10 years
Minimum | Furniture and Fixtures
Organization, Basis of Presentation and Summary of Significant Accounting Policies (Details) [Line Items]
PPE useful life (in years)	3 years
Maximum | Building
Organization, Basis of Presentation and Summary of Significant Accounting Policies (Details) [Line Items]
PPE useful life (in years)	40 years
Maximum | Building Improvements
Organization, Basis of Presentation and Summary of Significant Accounting Policies (Details) [Line Items]
PPE useful life (in years)	20 years
Maximum | Furniture and Fixtures
Organization, Basis of Presentation and Summary of Significant Accounting Policies (Details) [Line Items]
PPE useful life (in years)	10 years
Accounting Standards Update 2016-02
Organization, Basis of Presentation and Summary of Significant Accounting Policies (Details) [Line Items]
Lease liability				$ 18,000,000.0
Operating lease, right-of-use asset				$ 17,000,000.0