Significant Accounting Policies (Property and Equipment) (Details)	12 Months Ended
Dec. 31, 2017
Software and Software Development Costs
Property, Plant and Equipment [Line Items]
Useful life	3 years
Building \| Maximum
Property, Plant and Equipment [Line Items]
Useful life	40 years
Computer Equipment \| Maximum
Property, Plant and Equipment [Line Items]
Useful life	10 years
Computer Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Useful life	3 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