Earnings Per Share - Numerators and Denominators in Basic and Diluted Earnings (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 27, 2014	Sep. 24, 2016	Sep. 26, 2015	Sep. 27, 2014
Earnings Per Share [Abstract]
Net income (loss) available to common shareholders basic									$ 44,514	$ 31,971	$ 8,804
Net income (loss) available to common shareholders diluted									$ 44,514	$ 31,971	$ 8,804
Net income (loss) available to common shareholders basic (in shares)	49,453	49,120	48,717	48,566	48,322	48,167	48,384	49,379	48,964	48,562	48,880
Options to purchase common stock (in shares)									1,335	520	69
Restricted shares (in shares)									776	556	448
Net income (loss) available to common shareholders diluted (in shares)	49,453	51,063	50,445	48,566	48,322	49,290	49,439	49,379	51,075	49,638	49,397
Net income (loss) available to common shareholders basic (in usd per share)	$ (0.11)	$ 0.53	$ 0.67	$ (0.18)	$ (0.09)	$ 0.39	$ 0.48	$ (0.12)	$ 0.91	$ 0.66	$ 0.18
Options to purchase common stock (in usd per share)									(0.02)	(0.01)	0.00
Restricted shares (in usd per share)									(0.02)	(0.01)	0.00
Net income (loss) available to common shareholders diluted (in usd per share)	$ (0.11)	$ 0.51	$ 0.65	$ (0.18)	$ (0.09)	$ 0.38	$ 0.47	$ (0.12)	$ 0.87	$ 0.64	$ 0.18