Interim Condensed Consolidated Balance Sheets (Parenthetical) $ in Thousands	Mar. 29, 2019 USD ($) vote / shares $ / shares shares	Sep. 28, 2018 USD ($) vote / shares $ / shares shares
Allowance for doubtful accounts | $	$ (7,207)	$ (5,258)
Class A Common Stock [Member]
Common stock, par value (usd per share) | $ / shares	$ 0.001	$ 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)	63,979,294	63,978,752
Common stock, shares outstanding (shares)	63,979,294	63,978,752
Class B Common Stock [Member]
Common stock, par value (usd per share) | $ / shares	$ 0.001	$ 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)	37,635,152	39,261,035
Common stock, shares outstanding (shares)	37,635,152	39,261,035