Acquired Intangible Assets and Liabilities (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Amortization of below market leases	$ 1,800		$ 2,300
Expected average remaining lives of acquired below market leases (in years)	6 years 4 months
Amortization of intangible assets	$ 44,659		41,841
Acquired above-market leases
Finite-Lived Intangible Assets [Line Items]
Expected average remaining lives (in years)	4 years
Acquired in-place lease value
Finite-Lived Intangible Assets [Line Items]
Expected average remaining lives (in years)	7 years 11 months 20 days
Amortization of intangible assets	$ 14,200		13,700
Weighted average remaining contractual life for acquired leases excluding renewals or extensions (in years)	6 years 10 months 10 days
Tenant relationship value
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 17,600		15,900
Weighted average remaining contractual life for acquired leases excluding renewals or extensions (in years)	12 years 8 months 20 days
Trade name
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 0		$ 500
Write-down of intangible assets		$ 6,100