Shared-Based Compensation Shared-Based Compensation - Phantom (Details) - shares	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options granted	55,300	55,300

Net number of share options (or share units) granted during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration