Goodwill and Other Intangibles - Intangible Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Intangible lease liabilities:
Accumulated amortization	$ 65,174	$ 56,891
Weighted-Average Useful Life	18 years 3 months 2 days
Intangible lease liabilities, net	$ 209,566	224,023
Total Intangible Lease Assets [Member]
Intangible lease assets:
Intangible lease assets, net	1,370,972	1,478,884
In-Place Leases [Member]
Intangible lease assets:
Accumulated amortization	$ 549,208	494,131
Weighted-Average Useful Life	14 years 10 months
Intangible lease assets, net	$ 1,107,440	1,192,756
Leasing Commissions [Member]
Intangible lease assets:
Accumulated amortization	$ 2,321	1,836
Weighted-Average Useful Life	10 years 3 months 29 days
Intangible lease assets, net	$ 11,020	10,231
Above-Market Leases [Member]
Intangible lease assets:
Accumulated amortization	$ 77,791	69,670
Weighted-Average Useful Life	16 years 2 months 16 days
Intangible lease assets, net	$ 252,512	$ 275,897