Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.

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

Description of Business (Details) - segment	3 Months Ended		6 Months Ended
Description of Business (Details) - segment	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Description of Business
Number of reportable segments			2
BSI
Description of Business
Segment revenue (as a percent)	90.70%	87.40%	90.20%	88.60%