Summary of Significant Accounting Policies - Leasehold Improvements and Property and Equipment (Details) - Computer Hardware, Software, Furniture and Fixtures [Member]	12 Months Ended
Dec. 31, 2017
Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment estimated useful life	3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment estimated useful life	7 years

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

No definition available.

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