Foreign currency transaction realized and unrealized gain (loss) net of tax.

No definition available.

Name:	syna_ForeignCurrencyTransactionRealizedAndUnrealizedGainLossNetOfTax
Namespace Prefix:	syna_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Basis of Presentation - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Basis Of Presentation [Line Items]
Net gain (loss) on foreign currency transactions	$ (200,000)	$ (100,000)	$ (500,000)
Maximum [Member]
Basis Of Presentation [Line Items]
Net gain (loss) on foreign currency transactions				$ (100,000)