Information on Business Segments - Narrative (Detail) - segment	8 Months Ended	12 Months Ended			28 Months Ended
	Aug. 23, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Segment Reporting [Abstract]
Number of business segments		4
Net Sales | Product Concentration Risk | F-35 Program | Aeronautics
Segment Reporting Information [Line Items]
Net sales for the F-35 program representing total consolidated net sales (as a percent)		27.00%	26.00%	23.00%
AWE Management Limited | Net Earnings | Equity Method Investment Risk | Space
Segment Reporting Information [Line Items]
Concentration percentage	33.00%
AWE Management Limited | Net Sales | Equity Method Investment Risk | Space
Segment Reporting Information [Line Items]
Concentration percentage	0.00%
AWE Management Limited | Net Sales | Segment Concentration Risk | Space
Segment Reporting Information [Line Items]
Concentration percentage		100.00%			100.00%
AWE Management Limited | Operating profit | Segment Concentration Risk | Space
Segment Reporting Information [Line Items]
Concentration percentage		51.00%		51.00%	51.00%