Description of Company (Details)		12 Months Ended
Jul. 31, 2007	Dec. 31, 2018 segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Common stock distribution percentage due to spin-off	100.00%
Common stock distribution, due to spin-off, conversion ratio	3
Number of reportable segments		1

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