Intangible Assets and Liabilities - Annual Amortization of Intangible Assets, Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
2018	$ 14,948
2019	12,438
2020	9,770
2021	7,160
2022	5,093
Thereafter	15,563
Intangible Assets, net	64,972	$ 72,478
Liabilities
2018	3,553
2019	2,807
2020	2,042
2021	1,406
2022	1,238
Thereafter	9,228
Acquired Lease Intangibles, Net	$ 20,274	$ 18,119