Restructuring and Divestiture Charges - Charges Taken Related to Restructuring Actions (Detail) - USD ($) $ in Thousands	3 Months Ended							12 Months Ended
	Sep. 26, 2015	Jun. 27, 2015	Dec. 27, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 28, 2013	Sep. 26, 2015	Sep. 27, 2014	Sep. 28, 2013
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges								$ 0	$ 38,400	$ 9,400
Fiscal restructuring and divestiture charges	$ 6,500	$ 11,900	$ 8,000	$ 15,100	$ 6,700	$ 11,600	$ 18,400	28,500	51,700	32,800
Fiscal 2013 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges										(100)
Workforce reductions										31,200
Facility closure costs										600
Other										900
Fiscal restructuring charges										32,700
Divestiture net charges										112
Fiscal restructuring and divestiture charges										32,800
Fiscal 2014 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges									3,100
Workforce reductions									42,200
Facility closure costs									600
Other									300
Fiscal restructuring charges									46,200
Divestiture net charges									5,500
Fiscal restructuring and divestiture charges									51,700
Two Thousand Fifteen [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions								16,300
Facility closure costs								2,600
Fiscal restructuring charges								18,900
Divestiture net charges								9,600
Fiscal restructuring and divestiture charges								28,500
Consolidation of Diagnostics Operations [Member] | Fiscal 2013 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges										0
Workforce reductions										14,000
Facility closure costs										0
Other										0
Fiscal restructuring charges										14,000
Consolidation of Diagnostics Operations [Member] | Fiscal 2014 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges									0
Workforce reductions									2,900
Facility closure costs									0
Other									100
Fiscal restructuring charges									3,000
Consolidation of Diagnostics Operations [Member] | Two Thousand Fifteen [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions								100
Facility closure costs								500
Fiscal restructuring charges								600
Closure of Indianapolis Facility [Member] | Fiscal 2013 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges										0
Workforce reductions										4,800
Facility closure costs										200
Other										700
Fiscal restructuring charges										5,700
Closure of Indianapolis Facility [Member] | Fiscal 2014 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges									0
Workforce reductions									200
Facility closure costs									500
Other									0
Fiscal restructuring charges									700
Closure of Indianapolis Facility [Member] | Two Thousand Fifteen [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions								0
Facility closure costs								0
Fiscal restructuring charges								0
Restructuring Action Two Thousand Fifteen [Member] | Fiscal 2013 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges										0
Workforce reductions										0
Facility closure costs										0
Other										0
Fiscal restructuring charges										0
Restructuring Action Two Thousand Fifteen [Member] | Fiscal 2014 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges									0
Workforce reductions									0
Facility closure costs									0
Other									0
Fiscal restructuring charges									0
Restructuring Action Two Thousand Fifteen [Member] | Two Thousand Fifteen [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions								10,000
Facility closure costs								0
Fiscal restructuring charges								10,000
Fiscal 2014 Actions [Member] | Fiscal 2013 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges										0
Workforce reductions										0
Facility closure costs										0
Other										0
Fiscal restructuring charges										0
Fiscal 2014 Actions [Member] | Fiscal 2014 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges									0
Workforce reductions									29,500
Facility closure costs									0
Other									0
Fiscal restructuring charges									29,500
Fiscal 2014 Actions [Member] | Two Thousand Fifteen [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions								6,000
Facility closure costs								2,000
Fiscal restructuring charges								8,000
Fiscal 2013 Actions [Member] | Fiscal 2013 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges										0
Workforce reductions										11,300
Facility closure costs										0
Other										0
Fiscal restructuring charges										11,300
Fiscal 2013 Actions [Member] | Fiscal 2014 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges									0
Workforce reductions									900
Facility closure costs									0
Other									0
Fiscal restructuring charges									900
Fiscal 2013 Actions [Member] | Two Thousand Fifteen [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions								0
Facility closure costs								0
Fiscal restructuring charges								0
Other Operating Cost Reductions [Member] | Fiscal 2013 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges										(100)
Workforce reductions										1,100
Facility closure costs										400
Other										200
Fiscal restructuring charges										$ 1,700
Other Operating Cost Reductions [Member] | Fiscal 2014 Charges [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Non-cash impairment charges									3,100
Workforce reductions									8,700
Facility closure costs									100
Other									200
Fiscal restructuring charges									$ 12,100
Other Operating Cost Reductions [Member] | Two Thousand Fifteen [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Workforce reductions								200
Facility closure costs								100
Fiscal restructuring charges								$ 300