Stock-Based Compensation and Stock Plans - Narrative (Details) - USD ($)			3 Months Ended		12 Months Ended
	Nov. 04, 2016	Jun. 23, 2015	Sep. 29, 2018	Sep. 30, 2017	Jun. 30, 2018	Jul. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock authorized for issuance under plan (in shares)		8,500,000.0
Common stock reserved for future issuance (in shares)						2,100,000
Increase in number of shares that may be issued	3,000,000.0
Shares of common stock available for grant (in shares)			5,000,000		5,600,000
Stock-based compensation			$ 10,800,000	$ 9,300,000
Stock-based compensation capitalized to inventory			$ 2,100,000		$ 2,600,000
Options exercised (in shares)			40,270
Intrinsic value of options exercised			$ 700,000
Stock-based compensation cost related to awards granted to employees			$ 97,800,000
Estimated amortization period			2 years 1 month
Shares issued to employees (in shares)			0	0
Full Value Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Stock options issued and outstanding (in shares)			2,000,000
Full Value Awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Vesting period			1 year
Full Value Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Vesting period			4 years
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Shares of common stock available for grant (in shares)			5,000,000
Options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Vesting period			3 years
Stock awards expiration period			5 years
Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Vesting period			4 years
Stock awards expiration period			10 years
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Vesting period			3 years
RSUs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Vesting period			1 year
RSUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Vesting period			4 years
RSAs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Vesting period			1 year
RSAs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Vesting period			4 years
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock authorized for issuance under plan (in shares)			200,000
Vesting period			3 years
Stock-based compensation			$ 0
2015 Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line items]
Common stock authorized for issuance under plan (in shares)		3,000,000.0
Shares of common stock available for grant (in shares)			2,300,000
Stock-based compensation			$ 1,000,000	$ 800,000
Discount rate provided under purchase plan (as a percent)		15.00%
Look-back period		6 months