Impairments - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) property	Jun. 30, 2018 USD ($) property	Jun. 30, 2019 USD ($) property	Jun. 30, 2018 USD ($) property
Property, Plant and Equipment [Abstract]
Provisions for impairment | $	$ 13,061	$ 3,951	$ 17,733	$ 18,172
Number of impaired properties held for sale	8		10
Number of impaired properties held for investment	2	1	2	2
Number of impaired properties sold	4	17	12	23