The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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

Real Estate Assets (Details) $ in Thousands	3 Months Ended		6 Months Ended
Real Estate Assets (Details) $ in Thousands	Jun. 30, 2019 USD ($) propertyUnit	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) propertyUnit	Jun. 30, 2018 USD ($)
Dispositions [Abstract]
Gains on disposition of property	$ 6,703	$ 16,972	$ 6,703	$ 16,972
Impairments [Abstract]
Impairments of real estate assets	$ 531	$ 0	$ 531	$ 0
2019 Dispositions [Member]
Dispositions [Abstract]
Number of buildings sold \| propertyUnit	2		2
Purchase price of real estate	$ 32,500
Gains on disposition of property	6,700
2019 Impairments [Member]
Impairments [Abstract]
Impairments of real estate assets	$ 500