Commitments And Contingencies (Summary Of Properties Under Contracts) (Details) - 3 months ended Mar. 31, 2019 $ in Thousands	USD ($) a	property	ft²
Third-Party Seller [Member]
Real Estate Properties [Line Items]
Number of Buildings | property		2
Area of real estate property | ft²			116,600
Purchase price	$ 52,100
Assumed debt	0
Los Angeles [Member] | Third-Party Seller [Member]
Real Estate Properties [Line Items]
Number of Buildings | property		0
Area of real estate property | ft²			0
Purchase price	0
Assumed debt	0
Northern New Jersey/New York City [Member] | Third-Party Seller [Member]
Real Estate Properties [Line Items]
Number of Buildings | property		0
Area of real estate property | ft²			0
Purchase price	4,325
Assumed debt	0
San Francisco Bay Area [Member] | Third-Party Seller [Member]
Real Estate Properties [Line Items]
Number of Buildings | property		2
Area of real estate property | ft²			116,600
Purchase price	47,775
Assumed debt	0
Seattle [Member] | Third-Party Seller [Member]
Real Estate Properties [Line Items]
Number of Buildings | property		0
Area of real estate property | ft²			0
Purchase price	0
Assumed debt	0
Miami [Member] | Third-Party Seller [Member]
Real Estate Properties [Line Items]
Number of Buildings | property		0
Area of real estate property | ft²			0
Purchase price	0
Assumed debt	0
Washington D.C. [Member] | Third-Party Seller [Member]
Real Estate Properties [Line Items]
Number of Buildings | property		0
Area of real estate property | ft²			0
Purchase price	0
Assumed debt	$ 0
Improved land parcels [Member]
Real Estate Properties [Line Items]
Number of Buildings | property		18
Area of real estate property	2.0		12,900,000
Improved land parcels [Member] | Northern New Jersey/New York City [Member] | Third-Party Seller [Member]
Real Estate Properties [Line Items]
Number of Buildings | property		1