Employee Severance and Termination Costs - Additional Information (Detail) $ in Millions			3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 25, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 25, 2015 USD ($) Employees	Sep. 26, 2014 USD ($)	Sep. 25, 2015 USD ($) Employees	Sep. 26, 2014 USD ($)	Dec. 31, 2014 USD ($) Employees
Restructuring and Related Activities [Abstract]
Employee severance and other termination costs			$ 4	$ 3	$ 10	$ 23	$ 30
Number of employees terminated | Employees			740		740		2,000
Remaining balance of employee termination costs	$ 6	$ 11