Summary of Significant Accounting Policies (Impacts of the ASC 842 and ASC 450 Reserves) (Details) - COVID-19 - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
ASC 842 reserve, rental revenue	$ (610)	$ 9,718	$ 751	$ 16,937
Total impact	(620)	11,391	(1,498)	23,006
Collectibility of receivables
Financing Receivable, Allowance for Credit Loss [Line Items]
ASC 450 reserve, provision for (recovery of) doubtful accounts	$ (10)	$ 1,673	$ (2,249)	$ 6,069

Amount charged against operating income increasing loss contingency liability, after adjustments to reduce previously estimated charges.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14326-108349

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