Commitments and Contingencies - Litigation and Related Contingencies (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Legal
Litigation and Related Contingencies
Accruals for potential contingencies	$ 0.0	$ 0.0

Amount of loss contingency liability.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

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