Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017	Mar. 25, 2017
Accounts receivable allowance for doubtful accounts	$ 20,976	$ 21,436	$ 20,227
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common Stock
Common stock, shares outstanding (in shares)	12,145,135	12,160,023	12,176,787
Class A Common Stock
Common stock, shares outstanding (in shares)	38,171,595	38,019,736	37,731,149
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Class B Common Stock
Common stock, shares outstanding (in shares)	1,652,262	1,652,262	1,652,262
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01