Income Taxes - Change in Valuation Allowance (Details) - Valuation Allowance - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 148	$ 726
Decrease	1,304	(578)
Balance at end of period	$ 1,452	$ 148

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e32123-109318

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration