Income Taxes - Net Operating Loss Carry Forward (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Operating Loss Carryforwards [Line Items]
Market capitalization used in net operating loss analysis	$ 124.5
Annual limitation on usage of net operating losses	3.0
Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 210.3

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

Name:	us-gaap_OperatingLossCarryforwards
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant