Intangibles - Estimated Aggregate Amortization of Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Estimated aggregate amortization of Intangible Assets
Net intangible lease assets	$ 410,082	$ 479,805
Rental and Related Revenues(1)
Estimated aggregate amortization of Intangible Assets
2018	4,099
2019	4,102
2020	3,418
2021	3,401
2022	4,199
Thereafter	17,133
Net intangible lease assets	36,352
Operating Expense(2)
Estimated aggregate amortization of Intangible Assets
2018	763
2019	763
2020	759
2021	756
2022	756
Thereafter	31,782
Net intangible lease assets	35,579
Depreciation and Amortization(3)
Estimated aggregate amortization of Intangible Assets
2018	66,651
2019	49,868
2020	40,151
2021	35,963
2022	30,490
Thereafter	135,153
Net intangible lease assets	$ 358,276