Significant Accounting Policies Stock-based compensation (Details) - USD ($) $ in Thousands	12 Months Ended	77 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 30, 2018
Significant Accounting Policies [Abstract]
Stock-based Compensation	$ 1,212	$ 1,134	$ 1,184	$ 6,900

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Name:	us-gaap_ShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration