Income Taxes - Tax refund (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Income Taxes
Unrecognized tax benefits, income tax penalties accrued	$ 0.0	$ 0.0

Amount of statutory penalties accrued for a tax position claimed or expected to be claimed by the entity, in its tax return.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

Name:	us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAccrued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant