Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 20, 2016 USD ($) $ / Product	Sep. 23, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 23, 2016 USD ($) $ / shares	Sep. 25, 2015 USD ($) $ / shares	Dec. 31, 2015 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Percentage of net sales accounted for under contract accounting standards				50.00%		49.00%
Percentage of fixed-price type contracts						41.00%
Percentage of cost-plus type contracts						8.00%
Period of performance for contracts accounted for under the percentage-of-completion method of accounting, minimum				1 year
Increase in operating income due to changes in contract estimates				$ 127	$ 50
Percentage of increase in consolidated operating income due to changes in contract estimates				18.00%	9.00%
Increase in operating income due to changes in contract estimates, per diluted share | $ / shares				$ 1.03	$ 0.49
Product returns allowance		$ 8	$ 20	$ 8		$ 20
EoTech HWS [Member]
Summary Of Significant Accounting Policies [Line Items]
Total expected cost of the voluntary return program				36
Product returns allowance		8		8
EoTech HWS [Member] | Electronic Systems [Member]
Summary Of Significant Accounting Policies [Line Items]
Reduction to net sales			$ 20	$ 16
EoTech HWS [Member] | Electronic Systems [Member] | EoTech HWS Class Action [Member]
Summary Of Significant Accounting Policies [Line Items]
Pre-tax charge, litigation settlement		$ 14
Subsequent Event [Member] | EoTech HWS [Member]
Summary Of Significant Accounting Policies [Line Items]
Approved refunds cost	$ 32
Average refund cost per unit | $ / Product	500