Real Estate (Real Estate Dispositions) (Details) - Assets Held-for-sale $ 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
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of sold properties - gain on disposition of real estate \| property	13	13	30	28
Gain on disposition of real estate \| $	$ 13,002	$ 4,106	$ 23,447	$ 42,702

Amount of gain (loss) on sale or disposal of property, plant and equipment assets, excluding oil and gas property and timber property.

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 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2443-110228

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230

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Balance Type:	credit
Period Type:	duration