Balance sheet components - Property and equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 28, 2019	Sep. 29, 2018	Sep. 30, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 216,521	$ 197,605
Accumulated depreciation and amortization	(138,382)	(112,234)
Property and equipment, net	78,139	85,371
Depreciation	36,415	39,358	$ 35,014
Fixed asset, disposal	10,200	35,800	11,500
Fixed asset disposal, accumulated depreciation	9,300	35,600	11,200
Loss on disposal of fixed assets	800	200	$ 200
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	47,775	46,385
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	9,594	9,696
Tooling and production line test equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	54,536	47,297
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	58,944	53,962
Product displays
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 45,672	$ 40,265

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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- Definition

Amount of decrease in accumulated depreciation, depletion and amortization as a result of sale or disposal of property, plant and equipment.

+ References

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

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Amount of divestiture of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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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.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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