Intangible Assets and Liabilities - Annual Amortization of Intangible Assets, Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets
2019 (nine months remaining)	$ 30,532
2020	28,393
2021	20,128
2022	12,791
2023	9,756
Thereafter	18,303
Intangible Assets, net	119,903	$ 131,348
Liabilities
2019 (nine months remaining)	5,433
2020	5,707
2021	4,302
2022	2,654
2023	2,094
Thereafter	9,623
Acquired Lease Intangibles, Net	$ 29,813	$ 31,783