Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 26, 2015	Sep. 26, 2015	Dec. 27, 2014
Assets:
Total assets			$ 9,992
Liabilities:
Total liabilities	$ 5,625	$ 3,625	4,414
Liability for Contingent Consideration [Member]
Liabilities:
Total liabilities	5,625	3,625	4,414
Short Term Investments [Member]
Assets:
Total assets			9,992
Level 1 [Member]
Assets:
Total assets			9,992
Liabilities:
Total liabilities	0	0	0
Level 1 [Member] | Liability for Contingent Consideration [Member]
Liabilities:
Total liabilities	0	0	0
Level 1 [Member] | Short Term Investments [Member]
Assets:
Total assets			9,992
Level 2 [Member]
Assets:
Total assets			0
Liabilities:
Total liabilities	0	0	0
Level 2 [Member] | Liability for Contingent Consideration [Member]
Liabilities:
Total liabilities	0	0	0
Level 2 [Member] | Short Term Investments [Member]
Assets:
Total assets			0
Level 3 [Member]
Assets:
Total assets			0
Liabilities:
Total liabilities	5,625	3,625	4,414
Level 3 [Member] | Liability for Contingent Consideration [Member]
Liabilities:
Total liabilities	$ 5,625	$ 3,625	4,414
Level 3 [Member] | Short Term Investments [Member]
Assets:
Total assets			$ 0