Goodwill and Other Intangibles (Intangible Lease Assets and Liabilities) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Intangible lease liabilities, accumulated amortization	$ 52,027	$ 38,340
Below-market lease, Weighted-Average Useful Life	17 years 11 months 16 days	17 years 11 months 16 days
Intangible lease liabilities, net	$ 229,340	$ 251,692
Total Intangible Lease Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible lease assets, net	1,537,826	1,771,532
In-Place Leases [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible lease assets, accumulated amortization	$ 469,617	$ 398,770
Intangible lease assets, Weighted-Average Useful Life	14 years 9 months	14 years 9 months
Intangible lease assets, net	$ 1,246,392	$ 1,458,354
Leasing Commissions [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible lease assets, accumulated amortization	$ 1,681	$ 1,035
Intangible lease assets, Weighted-Average Useful Life	9 years 6 months 15 days	9 years 6 months 15 days
Intangible lease assets, net	$ 8,541	$ 4,872
Above-Market Leases [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible lease assets, accumulated amortization	$ 63,952	$ 47,041
Intangible lease assets, Weighted-Average Useful Life	16 years 7 months 6 days	16 years 7 months 6 days
Intangible lease assets, net	$ 282,893	$ 308,306