Share-Based Compensation - Market Stock Units - Additional Information (Detail) - Market stock units outstanding [Member] - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
Dec. 31, 2018	Dec. 28, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Potential payout adjustment ratio	200.00%
Closing price of common stock used to calculate Aggregate intrinsic value of stock option outstanding		$ 37.14
Shares withheld to meet statutory tax withholding requirements	33,981
Shares valued withheld to meet statutory tax withholding requirements	$ 1.3
Unrecognized share-based compensation cost	$ 16.8
Unrecognized share-based compensation, period for recognition	1 year 4 months 24 days
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Potential payout range	0.00%
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Potential payout range	200.00%
Share-based Compensation Award, First Tranche [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period of the underlying awards	1 year
Vesting percentage of the underlying awards	33.33%
Share-based Compensation Award, First Tranche [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Potential payout range	100.00%
Share-based Compensation Award, Second Tranche [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period of the underlying awards	2 years
Vesting percentage of the underlying awards	33.33%
Share-based Compensation Award, Second Tranche [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Potential payout range	100.00%
Share-based Compensation Award, Third Tranche [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period of the underlying awards	3 years
Vesting percentage of the underlying awards	33.33%

Percentage of potential payout.

No definition available.

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- Definition

Potential payout adjustment ratio.

+ References

No definition available.

+ Details

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- Definition

Share based compensation arrangement by share based payment award intrinsic value closing price.

+ References

No definition available.

+ Details

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Namespace Prefix:	syna_
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Period Type:	instant

- Definition

The amount of adjustment to stockholders' equity associated with an employee's income tax withholding obligation as part of a net-share settlement of a share-based award.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

+ Details

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

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Balance Type:	na
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

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Balance Type:	na
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- Definition

Percentage of vesting of share-based compensation awards.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

+ References

No definition available.

+ Details

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