Income Taxes - Uncertain Tax Positions (Details)	6 Months Ended
Jun. 30, 2018 USD ($)
Reconciliation of unrecognized tax benefits details [Abstract]
Changes in unrecognized tax benefits

Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

Name:	us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration