Preparation of Interim Financial Statements and Other Items - Significant Customers and Concentration of Credit Risk (Details) $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($) customer	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Total revenues \| Customer
Significant Customers and Concentration of Credit Risk
Number of Customers \| customer	1
Concentration of risk (as a percent)	10.00%	11.00%
Purchases \| Supplier concentration
Significant Customers and Concentration of Credit Risk
Concentration of risk (as a percent)	19.00%	21.00%
Purchases from the vendor	$ 23.0	$ 22.5
Accounts Payable	$ 7.3		$ 5.0

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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-Publisher FASB
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The number of customers with concentration risk.

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