Organization and Summary of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) segment tenant	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($) segment	Jan. 01, 2019 USD ($)
Debt Instrument [Line Items]
Number of operating segments | segment	1	1	1
Interest costs capitalized	$ 1,388,000	$ 1,099,000	$ 2,675,000
Real estate acquisitions	137,667,000	668,489,000
Investments in work in progress - improvements	42,300,000	84,008,000
Write-off of outstanding receivables and related accrued rent	$ 21,792,000
Percentage of total properties for which revenue recognized on cash basis	6.00%
Percentage of aggregate gross leasable area for which revenue recognized on cash basis	8.00%
Number of tenants for which revenue recognized on cash basis | tenant	13
Revenue recognized on cash basis	$ 4,722,000	0	$ 0
Revolving credit facility borrowing capacity	900,000,000
Deferred debt costs, accumulated amortization	$ 17,294,000	15,574,000
Land improvements
Debt Instrument [Line Items]
Property estimated useful life	15 years
Mortgage receivable
Debt Instrument [Line Items]
Mortgage receivable	$ 2,482,000	0
Allowance for credit loss	$ 158,000
Collectability analysis, period used	15 years
Minimum
Debt Instrument [Line Items]
Initial lease terms	10 years
Minimum | Buildings and improvements
Debt Instrument [Line Items]
Property estimated useful life	20 years
Maximum
Debt Instrument [Line Items]
Initial lease terms	20 years
Maximum | Buildings and improvements
Debt Instrument [Line Items]
Property estimated useful life	40 years
Mortgages
Debt Instrument [Line Items]
Deferred debt costs	$ 147,000	147,000
Deferred debt costs, accumulated amortization	108,000	90,000
Notes Payable
Debt Instrument [Line Items]
Deferred debt costs	31,140,000	26,932,000
Deferred debt costs, accumulated amortization	$ 9,317,000	$ 8,962,000
ASU 2016-02
Debt Instrument [Line Items]
Operating lease - right-of-use assets				$ 7,735,000
Operating lease liabilities				$ 10,155,000