Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 27, 2014	Sep. 27, 2014	Dec. 28, 2013
Assets:
Total assets	$ 9,992	$ 9,990	$ 14,220
Liabilities:
Total liabilities	4,414	4,414	4,165
Liability for Contingent Consideration [Member]
Liabilities:
Total liabilities	4,414	4,414	4,165
Certificates of Deposit [Member]
Assets:
Total assets			14,220
Short Term Investments [Member]
Assets:
Total assets	9,992	9,990
Level 1 [Member]
Assets:
Total assets	9,992	9,990	0
Liabilities:
Total liabilities	0	0	0
Level 1 [Member] | Liability for Contingent Consideration [Member]
Liabilities:
Total liabilities	0	0	0
Level 1 [Member] | Certificates of Deposit [Member]
Assets:
Total assets			0
Level 1 [Member] | Short Term Investments [Member]
Assets:
Total assets	9,992	9,990
Level 2 [Member]
Assets:
Total assets	0	0	14,220
Liabilities:
Total liabilities	0	0	0
Level 2 [Member] | Liability for Contingent Consideration [Member]
Liabilities:
Total liabilities	0	0	0
Level 2 [Member] | Certificates of Deposit [Member]
Assets:
Total assets			14,220
Level 2 [Member] | Short Term Investments [Member]
Assets:
Total assets	0	0
Level 3 [Member]
Assets:
Total assets	0	0	0
Liabilities:
Total liabilities	4,414	4,414	4,165
Level 3 [Member] | Liability for Contingent Consideration [Member]
Liabilities:
Total liabilities	4,414	4,414	4,165
Level 3 [Member] | Certificates of Deposit [Member]
Assets:
Total assets			0
Level 3 [Member] | Short Term Investments [Member]
Assets:
Total assets	$ 0	$ 0