Commitments and Contingencies - San Francisco Lease Termination (Details) - Subsequent event - Office lease - San Francisco office $ in Millions	1 Months Ended
Jul. 31, 2018 USD ($)
Operating Leased Assets [Line Items]
Decrease in future commitment	$ 4.5
Lease remaining term	6 years

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration