Commitments and Contingencies - Purchase Commitments Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) property agreement	Dec. 31, 2017 USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
Escrow deposits	$ 1,140	$ 4,995
Purchase Commitment [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of purchase and sale agreements | agreement	5
Percentage of voting interests acquired	100.00%
Number of properties acquired | property	8
Aggregate purchase price	$ 81,700
Escrow deposits	$ 1,100