Summary of Significant Accounting Policies - Inventory (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Inventory write-down	$ 5,400	$ 0

Amount of loss from reductions in inventory due to subsequent measurement adjustments, including, but not limited to, physical deterioration, obsolescence, or changes in price levels.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 35
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=68049868&loc=SL66093879-108312

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
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-Subparagraph (SX 210.5-03.2)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 35
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-URI http://asc.fasb.org/extlink&oid=68049868&loc=SL66093883-108312

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=66092785&loc=d3e4542-108314

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