Significant Accounting Policies - Receivables (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Significant Accounting Policies
Allowance for doubtful accounts receivable	$ 0.3	$ 0.2

Amount, after allowance for credit loss, of accounts and financing receivables, classified as current. Includes, but is not limited to, notes and loan receivable.

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Name:	us-gaap_AccountsNotesAndLoansReceivableNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant