Inventories - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Fixed Production Overhead To Cost Of Sales	$ 1,697	$ 3,794	$ 2,735
- Inventory provision (note 6)	$ 5,816	$ 651	$ 2,529

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://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116847112&loc=d3e4542-108314

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