Rental Property - Acquisitions - Allocation of Consideration (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($)
In-place leases
Allocation of the consideration paid for the acquired assets and liabilities
Deferred leasing intangibles	$ 40,857
Acquisitions 2017 [Member]
Allocation of the consideration paid for the acquired assets and liabilities
Land	39,900
Buildings	251,574
Tenant improvements	6,382
Building and land Improvements	22,754
Below market leases	(3,812)
Total purchase price	$ 385,393
Weighted average amortization period of below market leases	9 years
Acquisitions 2017 [Member] | In-place leases
Allocation of the consideration paid for the acquired assets and liabilities
Weighted average amortization period of lease intangibles	8 years 10 months 15 days
Acquisitions 2017 [Member] | Tenant relationships
Allocation of the consideration paid for the acquired assets and liabilities
Deferred leasing intangibles	$ 16,260
Weighted average amortization period of lease intangibles	11 years 2 months 20 days
Acquisitions 2017 [Member] | Above market leases
Allocation of the consideration paid for the acquired assets and liabilities
Deferred leasing intangibles	$ 11,478
Weighted average amortization period of lease intangibles	11 years 5 months 31 days