Impairments - (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019 USD ($) property	Sep. 30, 2018 USD ($) property	Sep. 30, 2019 USD ($) property	Sep. 30, 2018 USD ($) property
Provisions for impairment
Provisions for impairment \| $	$ 13,503	$ 6,862	$ 31,236	$ 25,034
Number of impaired properties held for sale	9	0	9	0
Number of impaired properties held for investment	2	1	4	3
Number of impaired properties sold	16	18	28	36

The charge against earnings in the period to reduce the carrying amount of real property to fair value.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2921-110230

Name:	us-gaap_ImpairmentOfRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration