Stockholders’ Equity - RSU activity (Details) - RSUs - $ / shares		12 Months Ended
	Oct. 01, 2018	Sep. 30, 2018	Sep. 30, 2017
Number of Shares
Balance unvested at the beginning of the period (in shares)	1,002,088	1,045,187	889,129
Granted (in shares)		344,433	395,913
Vested (in shares)		(147,832)	(158,243)
Forfeited (in shares)		(239,700)	(81,612)
Balance unvested at the end of the period (in shares)		1,002,088	1,045,187
Weighted Average Grant-Date Fair Value
Balance unvested at the beginning of the period (in dollars per share)	$ 50.32	$ 45.86	$ 45.98
Granted (in dollars per share)		61.19	46.20
Vested (in dollars per share)		46.88	46.15
Forfeited (in dollars per share)		48.42	48.32
Balance unvested at the end of the period (in dollars per share)		$ 50.32	$ 45.86
Shares available for future grants		536,067
Subsequent event
Number of Shares
Vested (in shares)	(128,947)