Business Segments (Details) $ in Millions	3 Months Ended			6 Months Ended
	Mar. 31, 2017 segment	Dec. 30, 2016 USD ($)	Jan. 01, 2016 USD ($)	Dec. 30, 2016 USD ($) segment	Jan. 01, 2016 USD ($)	Jul. 01, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment				4
Number of reportable segments | segment				4
Total assets		$ 11,618		$ 11,618		$ 11,993
Identifiable intangible assets		1,437		1,437		1,518
Income From Continuing Operations Before Income Taxes
Revenue		1,700	$ 1,748	3,378	$ 3,458
Non-operating income		1	0	2	1
Net interest expense		(43)	(46)	(87)	(92)
Income before income taxes		244	282	463	495
Business Segments (Textuals)
Cost of Goods and Services Sold		1,138	1,203	2,258	2,347
Operating Expenses		276	217	572	525
Amortization of intangible assets from Exelis Inc. acquisition				66	66
Scenario, Forecast
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Communication Systems | Workforce reductions, facility consolidation and other items [Member]
Income From Continuing Operations Before Income Taxes
Segment operating income			17		17
Business Segments (Textuals)
Cost of Goods and Services Sold			14		14
Operating Expenses			3		3
Critical Networks | Workforce reductions, facility consolidation and other items [Member]
Income From Continuing Operations Before Income Taxes
Segment operating income			4		4
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Total assets		3,013		3,013		3,268
Corporate Segment [Member] | Exelis
Business Segments (Textuals)
Business combination, integration and other costs		13	41	29	61
Amortization of intangible assets from Exelis Inc. acquisition		33	33	66	66
Operating Segments | Communication Systems
Segment Reporting Information [Line Items]
Total assets		1,606		1,606		1,667
Income From Continuing Operations Before Income Taxes
Revenue		413	489	843	943
Segment operating income		121	121	240	259
Operating Segments | Space and Intelligence Systems
Segment Reporting Information [Line Items]
Total assets		2,119		2,119		2,149
Income From Continuing Operations Before Income Taxes
Revenue		468	446	921	881
Segment operating income		77	68	157	135
Operating Segments | Electronic Systems
Segment Reporting Information [Line Items]
Total assets		2,241		2,241		2,253
Income From Continuing Operations Before Income Taxes
Revenue		384	381	745	756
Segment operating income		79	63	153	132
Operating Segments | Critical Networks
Segment Reporting Information [Line Items]
Total assets		2,639		2,639		2,656
Income From Continuing Operations Before Income Taxes
Revenue		454	446	905	910
Segment operating income		75	63	135	123
Corporate eliminations
Income From Continuing Operations Before Income Taxes
Revenue		(19)	(14)	(36)	(32)
Corporate eliminations		(1)	(1)	(2)	(2)
Business Segments (Textuals)
Net liability reduction for certain post-employment benefit plans			101		101
Corporate eliminations | Exelis
Segment Reporting Information [Line Items]
Identifiable intangible assets		1,400		1,400		$ 1,400
Unallocated corporate income (expense)
Income From Continuing Operations Before Income Taxes
Unallocated corporate income (expense)		$ (65)	$ 14	$ (135)	$ (61)