Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3367-108585

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RestructuringCostAndReserveLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 5.P.4(b))
-URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747

+ Details

Name:	us-gaap_RestructuringReserve
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of expense (reversal of expense) which increases (decreases) the restructuring reserve from an adjustment to a previously accrued restructuring liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 5.P.4(b)(2))
-URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747

+ Details

Name:	us-gaap_RestructuringReserveAccrualAdjustment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) in the accrual for restructuring costs.

+ References

+ Details

Name:	us-gaap_RestructuringReservePeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of decrease in the reserve for full or partial settlement through consideration other than cash.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 5.P.4(b)(2))
-URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

+ Details

Name:	us-gaap_RestructuringReserveSettledWithoutCash2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_RestructuringPlanAxis=syna_TwoThousandNineteenRestructuringPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=syna_EmployeeSeveranceAndBenefitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringPlanAxis=syna_NovemberTwoThousandSeventeenAndAprilTwoThousandEighteenRestructuringPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=syna_FacilityConsolidationAndRelatedChargesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringPlanAxis=syna_JuneTwoThousandSixteenRestructuringPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Restructuring Activities - Restructuring Liability Activities (Detail) - USD ($) $ in Millions	12 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 24, 2017	Jun. 25, 2016
2019 Restructuring Plan [Member] \| Employee Severance and Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Additional accruals	$ 17.7
Cash payments	(12.5)
Ending Balance	5.2
November 2017 and April 2018 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Beginning Balance	2.3
Additional accruals	0.2	$ 12.0
Cash payments	(2.5)	(9.0)
Non-cash settlements		(0.7)
Ending Balance		2.3
November 2017 and April 2018 Restructuring Plan [Member] \| Employee Severance and Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Beginning Balance	2.2
Additional accruals	0.2	11.0
Cash payments	(2.4)	(8.8)
Ending Balance		2.2
November 2017 and April 2018 Restructuring Plan [Member] \| Facility Consolidation and Related Charges [Member]
Restructuring Cost And Reserve [Line Items]
Beginning Balance	0.1
Additional accruals		1.0
Cash payments	$ (0.1)	(0.2)
Non-cash settlements		(0.7)
Ending Balance		0.1
June 2016 Restructuring Plan [Member]
Restructuring Cost And Reserve [Line Items]
Beginning Balance		0.6	$ 6.7
Additional accruals			7.3	$ 6.7
Adjustments		(0.2)
Cash payments		(0.4)	(12.6)
Non-cash settlements			(0.8)
Ending Balance			0.6	6.7
June 2016 Restructuring Plan [Member] \| Employee Severance and Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Beginning Balance			6.7
Additional accruals			5.0	6.7
Cash payments			(11.7)
Ending Balance				$ 6.7
June 2016 Restructuring Plan [Member] \| Facility Consolidation and Related Charges [Member]
Restructuring Cost And Reserve [Line Items]
Beginning Balance		0.6
Additional accruals			2.3
Adjustments		(0.2)
Cash payments		$ (0.4)	(0.9)
Non-cash settlements			(0.8)
Ending Balance			$ 0.6