Summary of Significant Accounting Policies (Narrative) (Details)	3 Months Ended
Mar. 31, 2020 USD ($) segment	Mar. 31, 2019 USD ($)
Revenue from External Customer [Line Items]
Revenues	$ 17,890,000	$ 17,991,000
Uncertain tax positions	$ 0
Number of operating segments \| segment	1
Bill and Hold Arrangement
Revenue from External Customer [Line Items]
Revenues	$ 852,000,000	$ 2,700,000
Minimum
Revenue from External Customer [Line Items]
Amortization period of capitalized contract costs	1 year
Property and equipment, estimated useful life	3 years
Maximum
Revenue from External Customer [Line Items]
Property and equipment, estimated useful life	39 years
Rental Equipment \| Minimum
Revenue from External Customer [Line Items]
Property and equipment, estimated useful life	15 years
Rental Equipment \| Maximum
Revenue from External Customer [Line Items]
Property and equipment, estimated useful life	25 years

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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