Operating Segments - Narrative (Details)	12 Months Ended
Dec. 31, 2017 segments
Segment Reporting [Abstract]
Number of operating segment	2

Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment.

No definition available.

Name:	us-gaap_NumberOfReportingUnits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration