Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2018		Apr. 01, 2018	[2]	Dec. 31, 2017		Oct. 01, 2017	Dec. 31, 2016
Current assets:
Cash and equivalents	$ 1,010				$ 2,983		$ 2,722	$ 2,334
Accounts receivable	3,736				3,617
Unbilled receivables	7,564				5,240
Inventories	6,247				5,303
Other current assets	1,401				1,185
Total current assets	19,958				18,328
Noncurrent assets:
Property, plant and equipment (PP&E)	9,274				8,237
Accumulated depreciation of PP&E	(5,030)				(4,720)
Intangible assets, net	2,667				702
Goodwill	19,486	[1]	$ 11,955		11,914	[2]
Other assets	608				585
Net investment in subsidiaries	0				0
Total noncurrent assets	27,005				16,718
Total assets	46,963				35,046
Current liabilities:
Short-term debt and current portion of long-term debt	1,678				2
Customer advances and deposits	7,327				6,992
Other current liabilities	6,684				6,105
Total current liabilities	15,689				13,099
Noncurrent liabilities:
Long-term debt	11,403				3,980
Other liabilities	7,116				6,532
Total noncurrent liabilities	18,519				10,512
Total shareholders’ equity	12,755				11,435		11,564	10,301
Total liabilities and shareholders’ equity	46,963				35,046
Consolidating Adjustments
Current assets:
Cash and equivalents	0				0		0	0
Accounts receivable	0				0
Unbilled receivables	0				0
Inventories	0				0
Other current assets	0				0
Total current assets	0				0
Noncurrent assets:
Property, plant and equipment (PP&E)	0				0
Accumulated depreciation of PP&E	0				0
Intangible assets, net	0				0
Goodwill	0				0
Other assets	0				0
Net investment in subsidiaries	(27,308)				(15,771)
Total noncurrent assets	(27,308)				(15,771)
Total assets	(27,308)				(15,771)
Current liabilities:
Short-term debt and current portion of long-term debt	0				0
Customer advances and deposits	0				0
Other current liabilities	0				0
Total current liabilities	0				0
Noncurrent liabilities:
Long-term debt	0				0
Other liabilities	0				0
Total noncurrent liabilities	0				0
Total shareholders’ equity	(27,308)				(15,771)
Total liabilities and shareholders’ equity	(27,308)				(15,771)
Parent Company
Current assets:
Cash and equivalents	649				1,930		1,571	1,254
Accounts receivable	0				0
Unbilled receivables	0				0
Inventories	0				0
Other current assets	8				351
Total current assets	657				2,281
Noncurrent assets:
Property, plant and equipment (PP&E)	254				221
Accumulated depreciation of PP&E	(81)				(75)
Intangible assets, net	0				0
Goodwill	0				0
Other assets	201				199
Net investment in subsidiaries	27,308				15,771
Total noncurrent assets	27,682				16,116
Total assets	28,339				18,397
Current liabilities:
Short-term debt and current portion of long-term debt	1,671				0
Customer advances and deposits	0				0
Other current liabilities	586				561
Total current liabilities	2,257				561
Noncurrent liabilities:
Long-term debt	11,391				3,950
Other liabilities	1,936				2,451
Total noncurrent liabilities	13,327				6,401
Total shareholders’ equity	12,755				11,435
Total liabilities and shareholders’ equity	28,339				18,397
Guarantor Subsidiaries
Current assets:
Cash and equivalents	0				0		0	0
Accounts receivable	1,054				1,259
Unbilled receivables	2,848				2,547
Inventories	6,094				5,216
Other current assets	877				461
Total current assets	10,873				9,483
Noncurrent assets:
Property, plant and equipment (PP&E)	7,127				6,779
Accumulated depreciation of PP&E	(4,089)				(3,869)
Intangible assets, net	266				287
Goodwill	7,991				8,320
Other assets	229				232
Net investment in subsidiaries	0				0
Total noncurrent assets	11,524				11,749
Total assets	22,397				21,232
Current liabilities:
Short-term debt and current portion of long-term debt	1				1
Customer advances and deposits	4,496				4,180
Other current liabilities	3,881				3,758
Total current liabilities	8,378				7,939
Noncurrent liabilities:
Long-term debt	5				21
Other liabilities	3,514				3,473
Total noncurrent liabilities	3,519				3,494
Total shareholders’ equity	10,500				9,799
Total liabilities and shareholders’ equity	22,397				21,232
Non-Guarantor Subsidiaries
Current assets:
Cash and equivalents	361				1,053		$ 1,151	$ 1,080
Accounts receivable	2,682				2,358
Unbilled receivables	4,716				2,693
Inventories	153				87
Other current assets	516				373
Total current assets	8,428				6,564
Noncurrent assets:
Property, plant and equipment (PP&E)	1,893				1,237
Accumulated depreciation of PP&E	(860)				(776)
Intangible assets, net	2,401				415
Goodwill	11,495				3,594
Other assets	178				154
Net investment in subsidiaries	0				0
Total noncurrent assets	15,107				4,624
Total assets	23,535				11,188
Current liabilities:
Short-term debt and current portion of long-term debt	6				1
Customer advances and deposits	2,831				2,812
Other current liabilities	2,217				1,786
Total current liabilities	5,054				4,599
Noncurrent liabilities:
Long-term debt	7				9
Other liabilities	1,666				608
Total noncurrent liabilities	1,673				617
Total shareholders’ equity	16,808				5,972
Total liabilities and shareholders’ equity	$ 23,535				$ 11,188

[1] Goodwill in the Information Technology and Mission Systems reporting units is net of $526 and $1.3 billion of accumulated impairment losses, respectively.

[2] Goodwill in the Information Systems and Technology reporting unit is net of $1.9 billion of accumulated impairment losses.