Organization and Summary of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($) segment	Jan. 01, 2019 USD ($)	Oct. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)
Debt Instrument [Line Items]
Number of operating segments | segment	1	1	1
Interest costs capitalized	$ 1,099,000	$ 2,675,000	$ 2,435,000
Real estate acquisitions	668,489,000	591,691,000
Investments in work in progress - improvements	84,008,000	123,881,000
Revolving credit facility borrowing capacity	900,000,000				$ 900,000,000	$ 650,000,000
Deferred debt costs, accumulated amortization	15,574,000	14,118,000
Mortgages
Debt Instrument [Line Items]
Deferred debt costs	147,000	147,000
Deferred debt costs, accumulated amortization	90,000	73,000
Loans Payable
Debt Instrument [Line Items]
Deferred debt costs	26,932,000	26,932,000
Deferred debt costs, accumulated amortization	$ 8,962,000	$ 6,705,000
ASU 2016-02
Debt Instrument [Line Items]
Operating lease - right-of-use assets				$ 7,735,000
Operating lease liabilities				$ 10,155,000