Restructuring and Divestiture Charges - Additional Information (Detail)	3 Months Ended								6 Months Ended	12 Months Ended
	Jun. 27, 2015 USD ($)	Dec. 27, 2014 USD ($)	Sep. 27, 2014 USD ($)	Dec. 28, 2013 USD ($) employee	Sep. 28, 2013 USD ($)	Jun. 29, 2013 USD ($)	Mar. 30, 2013 USD ($)	Sep. 29, 2012 USD ($)	Mar. 29, 2014 USD ($)	Sep. 26, 2015 USD ($)	Sep. 27, 2014 USD ($)	Sep. 28, 2013 USD ($)	Sep. 29, 2012 USD ($)
Restructuring Cost and Reserve [Line Items]
Impairment charges of equipment fair value				$ 3,100,000								$ 5,000,000
Loss on sale of business			$ 5,300,000							$ (9,600,000)	$ (5,500,000)	0
Restructuring Reserve, Translation and Other Adjustment	$ 9,600,000
Bedford Closure [Domain]
Restructuring Cost and Reserve [Line Items]
Estimated aggregate severance charges										3,000,000
Restructuring Charges [Member] | Two Thousand Fifteen [Member]
Restructuring Cost and Reserve [Line Items]
Facility Closure Costs										2,600,000
Reduction Of Workforce Expenses										16,300,000
Share Based Compensation Expense Included Other Restructuring Costs										(4,100,000)
Consolidation of Diagnostics Operations [Member]
Restructuring Cost and Reserve [Line Items]
Severance charges									$ 0	0
Employee retention program, payments in cash							$ 9,700,000
Consolidation of Diagnostics Operations [Member] | Molecular Diagnostics Operations [Member]
Restructuring Cost and Reserve [Line Items]
Severance charges										100,000	3,000,000	3,200,000	$ 900,000
Facility Closure Costs										500,000
Exiting charges								$ 600,000
Consolidation of Diagnostics Operations [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Severance charges												10,800,000	13,300,000
Compensation charges												6,300,000	3,500,000
Consolidation of Diagnostics Operations [Member] | Restructuring Charges [Member] | Two Thousand Fifteen [Member]
Restructuring Cost and Reserve [Line Items]
Facility Closure Costs										500,000
Reduction Of Workforce Expenses										100,000
Share Based Compensation Expense Included Other Restructuring Costs										0
Closure of Indianapolis Facility [Member]
Restructuring Cost and Reserve [Line Items]
Severance charges										0	5,900,000
Closure of Indianapolis Facility [Member] | Restructuring Charges [Member]
Restructuring Cost and Reserve [Line Items]
Severance charges											200,000	4,800,000	900,000
Exiting charges												$ 800,000	$ 900,000
Other restructuring charges				400,000
Closure of Indianapolis Facility [Member] | Restructuring Charges [Member] | Two Thousand Fifteen [Member]
Restructuring Cost and Reserve [Line Items]
Facility Closure Costs										0
Reduction Of Workforce Expenses										0
Share Based Compensation Expense Included Other Restructuring Costs										0
Restructuring Action Two Thousand Fifteen [Member] | Restructuring Charges [Member] | Two Thousand Fifteen [Member]
Restructuring Cost and Reserve [Line Items]
Facility Closure Costs										0
Compensation charges										4,100,000
Reduction Of Workforce Expenses										10,000,000
Share Based Compensation Expense Included Other Restructuring Costs										(4,100,000)
Fiscal 2014 Actions [Member]
Restructuring Cost and Reserve [Line Items]
Severance charges				6,300,000						16,600,000
Compensation charges				400,000						1,800,000
Fiscal 2014 Actions [Member] | Jack Cumming [Member]
Restructuring Cost and Reserve [Line Items]
Severance charges				6,600,000
Compensation charges				$ 4,400,000
Fiscal 2014 Actions [Member] | Restructuring Charges [Member] | Two Thousand Fifteen [Member]
Restructuring Cost and Reserve [Line Items]
Facility Closure Costs										2,000,000
Number Office Locations related to Facility Closure Costs		0
Reduction Of Workforce Expenses										6,000,000
Share Based Compensation Expense Included Other Restructuring Costs										0
Fiscal 2013 Actions [Member]
Restructuring Cost and Reserve [Line Items]
Severance charges					$ 6,800,000	$ 4,600,000					900,000
Compensation charges					$ 1,400,000
Estimated aggregate severance charges										5,400,000
Fiscal 2013 Actions [Member] | Restructuring Charges [Member] | Two Thousand Fifteen [Member]
Restructuring Cost and Reserve [Line Items]
Facility Closure Costs										0
Reduction Of Workforce Expenses										0
Share Based Compensation Expense Included Other Restructuring Costs										0
Other Operating Cost Reductions [Member]
Restructuring Cost and Reserve [Line Items]
Severance charges										300,000	$ 8,700,000
Number of employees affected for severance benefits | employee				95
Impairment charges of equipment fair value				$ 3,100,000
Other Operating Cost Reductions [Member] | Restructuring Charges [Member] | Two Thousand Fifteen [Member]
Restructuring Cost and Reserve [Line Items]
Facility Closure Costs										100,000
Reduction Of Workforce Expenses										200,000
Share Based Compensation Expense Included Other Restructuring Costs										$ 0