Income Taxes - Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1	$ 0	$ 0
Additions based on tax positions related to prior years	2,906,000	0
Balance at December 31	$ 2,906,000	$ 0

Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration