Acquired In-Place Leases and Above/Below Market Leases Increases (Decreases) in Net Income as Result of Amortization of In-Place Leases Above Market Leases and Below Market Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of leases	$ (5,464)	$ (558)	$ (1,848)
Amortization of below market leases	4,239	4,719	4,686
In-place leases
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of leases	(8,769)	(4,029)	(4,767)
Above market leases
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of leases	$ (934)	$ (1,248)	$ (1,767)