Recast 2017 Financial Information (Details 2) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents	$ 1,228	$ 11,225	$ 1,878	$ 2,541
Accounts receivable, net	1,702	1,054
Unbilled receivables, net	5,600	3,465
Inventoried costs, net	719	398
Prepaid expenses and other current assets	883	445
Total current assets	10,132	16,587
Property, plant and equipment, net of accumulated depreciation of $5,066 for 2017	6,025	4,225
Goodwill	18,642	12,455
Deferred tax assets	69	447
Intangible Assets, net	1,460	52
Other non-current assets	1,615	1,362
Total assets	37,943	35,128
Trade accounts payable	1,939	1,661
Accrued employee compensation	1,645	1,382
Advance payments and amounts in excess of costs incurred	1,686	1,761
Other current liabilities	2,769	2,288
Total current liabilities	8,039	7,092
Long-term debt, net of current portion of $867 for 2017	13,889	14,399
Pension and other post-retirement benefit plan liabilities	5,394	5,511
Other non-current liabilities	1,518	994
Total liabilities	28,840	27,996
Commitments and Contingencies
Preferred stock, $1 par value; 10,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $1 par value; 800,000,000 shares authorized; issues and outstanding: 2017 - 174,085,619	174	174
Paid-in capital	0	44
Retained earnings	14,464	11,632
Accumulated other comprehensive loss	(5,535)	(4,718)
Total shareholders’ equity	9,103	7,132	$ 6,608
Total liabilities and shareholders’ equity	$ 37,943	35,128
Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents		11,225
Accounts receivable, net		829
Unbilled receivables, net		3,147
Inventoried costs, net		780
Prepaid expenses and other current assets		368
Total current assets		16,349
Property, plant and equipment, net of accumulated depreciation of $5,066 for 2017		4,225
Goodwill		12,455
Deferred tax assets		475
Intangible Assets, net		52
Other non-current assets		1,361
Total assets		34,917
Trade accounts payable		1,661
Accrued employee compensation		1,382
Advance payments and amounts in excess of costs incurred		1,617
Other current liabilities		2,305
Total current liabilities		6,965
Long-term debt, net of current portion of $867 for 2017		14,399
Pension and other post-retirement benefit plan liabilities		5,511
Other non-current liabilities		994
Total liabilities		27,869
Preferred stock, $1 par value; 10,000,000 shares authorized; no shares issued and outstanding		0
Common stock, $1 par value; 800,000,000 shares authorized; issues and outstanding: 2017 - 174,085,619		174
Paid-in capital		44
Retained earnings		11,548
Accumulated other comprehensive loss		(4,718)
Total shareholders’ equity		7,048
Total liabilities and shareholders’ equity		34,917
Restatement Adjustment [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents		0
Accounts receivable, net		225
Unbilled receivables, net		318
Inventoried costs, net		(382)
Prepaid expenses and other current assets		77
Total current assets		238
Property, plant and equipment, net of accumulated depreciation of $5,066 for 2017		0
Goodwill		0
Deferred tax assets		(28)
Intangible Assets, net		0
Other non-current assets		1
Total assets		211
Trade accounts payable		0
Accrued employee compensation		0
Advance payments and amounts in excess of costs incurred		144
Other current liabilities		(17)
Total current liabilities		127
Long-term debt, net of current portion of $867 for 2017		0
Pension and other post-retirement benefit plan liabilities		0
Other non-current liabilities		0
Total liabilities		127
Preferred stock, $1 par value; 10,000,000 shares authorized; no shares issued and outstanding		0
Common stock, $1 par value; 800,000,000 shares authorized; issues and outstanding: 2017 - 174,085,619		0
Paid-in capital		0
Retained earnings		84
Accumulated other comprehensive loss		0
Total shareholders’ equity		84
Total liabilities and shareholders’ equity		211
Restatement Adjustment [Member] | Accounting Standards Update 2017-07 [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash and cash equivalents		0
Accounts receivable, net		0
Unbilled receivables, net		0
Inventoried costs, net		0
Prepaid expenses and other current assets		0
Total current assets		0
Property, plant and equipment, net of accumulated depreciation of $5,066 for 2017		0
Goodwill		0
Deferred tax assets		0
Intangible Assets, net		0
Other non-current assets		0
Total assets		0
Trade accounts payable		0
Accrued employee compensation		0
Advance payments and amounts in excess of costs incurred		0
Other current liabilities		0
Total current liabilities		0
Long-term debt, net of current portion of $867 for 2017		0
Pension and other post-retirement benefit plan liabilities		0
Other non-current liabilities		0
Total liabilities		0
Preferred stock, $1 par value; 10,000,000 shares authorized; no shares issued and outstanding		0
Common stock, $1 par value; 800,000,000 shares authorized; issues and outstanding: 2017 - 174,085,619		0
Paid-in capital		0
Retained earnings		0
Accumulated other comprehensive loss		0
Total shareholders’ equity		0
Total liabilities and shareholders’ equity		$ 0