Basis of Presentation - Additional Information (Detail) - AWE Management Limited	3 Months Ended		6 Months Ended
	Jun. 25, 2017	Jun. 26, 2016	Jun. 25, 2017	Jun. 26, 2016	Aug. 24, 2016
Basis of Presentation [Line Items]
Ownership interest percentage owned immediately before acquisition					33.00%
Ownership interest percentage owned including subsequent acquisition					51.00%
Net Sales | Segment Concentration Risk | Space Systems
Basis of Presentation [Line Items]
Concentration percentage	100.00%		100.00%
Net Sales | Equity Method Investment Risk | Space Systems
Basis of Presentation [Line Items]
Concentration percentage		0.00%		0.00%
Operating profit | Segment Concentration Risk | Space Systems
Basis of Presentation [Line Items]
Concentration percentage	51.00%		51.00%
Net Earnings | Equity Method Investment Risk | Space Systems
Basis of Presentation [Line Items]
Concentration percentage		33.00%		33.00%