Intangible Assets and Liabilities - Annual Amortization of Intangible Assets, Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets
2018 (nine months remaining)	$ 11,483
2019	13,130
2020	10,452
2021	7,538
2022	5,355
Thereafter	15,656
Intangible Assets, net	63,614	$ 64,972
Liabilities
2018 (nine months remaining)	2,648
2019	2,847
2020	2,081
2021	1,432
2022	1,264
Thereafter	9,238
Acquired Lease Intangibles, Net	$ 19,510	$ 20,274