Interim Condensed Consolidated Balance Sheets (Parenthetical) $ in Thousands	Dec. 29, 2017 USD ($) vote / shares $ / shares shares	Sep. 29, 2017 USD ($) vote / shares $ / shares shares
Allowance for doubtful accounts | $	$ (4,087)	$ (2,967)
Class A Common Stock [Member]
Common stock, par value (usd per share) | $ / shares	$ 0.001
Common stock voting right per share (votes per share) | vote / shares	1	1
Common stock, shares authorized (shares)	500,000,000	500,000,000
Common stock, shares issued (shares)	60,541,095	59,281,837
Common stock, shares outstanding (shares)	60,541,095	59,281,837
Class B Common Stock [Member]
Common stock, par value (usd per share) | $ / shares		$ 0.001
Common stock voting right per share (votes per share) | vote / shares	10	10
Common stock, shares authorized (shares)	500,000,000	500,000,000
Common stock, shares issued (shares)	42,733,597	42,873,597
Common stock, shares outstanding (shares)	42,733,597	42,873,597