Goodwill and Other Intangibles (Intangible Lease Assets and Liabilities) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Intangible lease liabilities, accumulated amortization	$ 47,309	$ 38,340
Below-market lease, Weighted-Average Useful Life	18 years 1 month 17 days	18 years 1 month 17 days
Intangible lease liabilities, net	$ 237,403	$ 251,692
Total Intangible Lease Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible lease assets, net	1,603,846	1,771,532
In-Place Leases [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible lease assets, accumulated amortization	$ 439,249	$ 398,770
Intangible lease assets, Weighted-Average Useful Life	14 years 10 months 24 days	14 years 10 months 24 days
Intangible lease assets, net	$ 1,306,345	$ 1,458,354
Leasing Commissions [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible lease assets, accumulated amortization	$ 1,428	$ 1,035
Intangible lease assets, Weighted-Average Useful Life	9 years 2 months 12 days	9 years 2 months 12 days
Intangible lease assets, net	$ 6,647	$ 4,872
Above-Market Leases [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible lease assets, accumulated amortization	$ 58,083	$ 47,041
Intangible lease assets, Weighted-Average Useful Life	16 years 7 months 28 days	16 years 7 months 28 days
Intangible lease assets, net	$ 290,854	$ 308,306