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Inventories - Additional Information (Detail) $ in Millions | 6 Months Ended
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Dec. 31, 2019 USD ($)
Inventory Disclosure [Abstract] |
Transfer of inventory to current assets held for sale | $ 20.9

X
- Definition Transfer of inventory to current assets held for sale. + References No definition available. + Details
Name: | syna_TransferOfInventoryToCurrentAssetsHeldForSale
Namespace Prefix: | syna_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_InventoryDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration