Pension and Other Employee Benefits (Narrative) (Details)	3 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016	Jul. 31, 2018 USD ($)
Defined Benefit Plans and PRB Plans [Line Items]
Defined Contribution Plan, expense for contributions		$ 357,000,000	$ 326,000,000	$ 303,000,000
Amount invested in defined contribution plan		20,600,000,000	17,000,000,000.0
Discretionary pension contributions	$ 1,250,000,000	0	1,250,000,000	1,000,000,000
Net Periodic Benefit Cost (Credit), Loss Due to Settlement	288,000,000
Net Periodic Benefit Cost (Credit), Loss Due to Settlement, Net of Tax	228,000,000
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation		27,994,000,000	24,561,000,000
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets		20,146,000,000	18,300,000,000
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation		25,313,000,000	22,554,000,000
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets		20,146,000,000	18,300,000,000
Accumulated Benefit Obligation (ABO)		$ 26,307,000,000	23,447,000,000
Health care trend rate increase or decrease		1.00%
Effect of a 1% increase in assumed health care trend rate - accumulated postretirement benefit obligation		$ 4,000,000
Effect of a 1% decrease in assumed health care trend rate - accumulated postretirement benefit obligation		4,000,000
Defined Benefit Plan Assets invested in seven indices		4,600,000,000
FMV of Plan's derivatives		(8,000,000)	6,000,000
Pension Plan [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined benefit plan, liabilities, noncurrent		7,687,000,000	6,111,000,000
Defined Benefit Plan, Amount of Current Year Discretionary Contribution Elected to Apply to Offset Required Contributions in Next Two Fiscal Years	$ 1,000,000,000
Required contributions to pension plans expected		319,000,000
Net Periodic Benefit Expense (Income)		1,086,000,000	1,716,000,000	1,367,000,000
Projected benefit obligation		28,990,000,000	25,456,000,000	28,569,000,000
Net Periodic Benefit Cost (Credit), Loss Due to Settlement		$ 1,000,000	$ 286,000,000	$ 1,000,000
Discount rate		3.25%	4.28%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		7.38%	7.38%	7.39%
Defined Benefit Plan, Plan Assets, Amount		$ 21,317,000,000	$ 19,321,000,000	$ 21,002,000,000
Certain pension plans included as part of group annuity contract transfer [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Projected benefit obligation						$ 923,000,000
Group Annuity Contract, Number of U.S. Retirees and Beneficiaries						13,000
PRB [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined benefit plan, liabilities, noncurrent		369,000,000	354,000,000
Required contributions to pension plans expected		50,000,000
Net Periodic Benefit Expense (Income)		25,000,000	23,000,000	25,000,000
Projected benefit obligation		711,000,000	672,000,000	745,000,000
Net Periodic Benefit Cost (Credit), Loss Due to Settlement		$ 2,000,000	$ 1,000,000	$ 1,000,000
Discount rate		3.29%	4.31%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		6.25%	6.25%	6.25%
Defined Benefit Plan, Plan Assets, Amount		$ 324,000,000	$ 300,000,000	$ 358,000,000
UNITED STATES
Defined Benefit Plans and PRB Plans [Line Items]
Projected benefit obligation		$ 28,108,000,000	$ 24,656,000,000
Discount rate		3.29%	4.33%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		7.50%	7.50%	7.50%	8.00%
Actual return on assets		19.00%	(4.00%)	15.00%
Defined Benefit Plan, Plan Assets, Amount		$ 20,366,000,000	$ 18,488,000,000
Foreign Plan [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Net Periodic Benefit Expense (Income)		(3,000,000)	(8,000,000)	$ 2,000,000
Projected benefit obligation		882,000,000	800,000,000
Defined Benefit Plan, Plan Assets, Amount		$ 951,000,000	$ 833,000,000
50th percentile [Member] | UNITED STATES
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		6.53%	6.74%	6.89%
Executive Officer [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined benefit plan, liabilities, noncurrent		$ 39,000,000	$ 36,000,000
Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Marketable securities held in trust		753,000,000	642,000,000
Level 1 [Member] | UNITED STATES
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount		6,113,000,000	7,206,000,000
Level 3 [Member] | VEBA [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount		0	0
Level 3 [Member] | UNITED STATES
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount		32,000,000	31,000,000
Nonqualified Plan [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Liabilities related to nonqualified defined contribution plan		489,000,000	431,000,000
Nonqualified Plan [Member] | Level 1 [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Marketable securities held in trust		476,000,000	420,000,000
Raytheon Stock Fund [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Amount invested in defined contribution plan		$ 2,100,000,000	1,600,000,000
Minimum [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Percent company matches employees 401(K) contributions		3.00%
Maximum [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Percent company matches employees 401(K) contributions		4.00%
Effect of a 1% increase in assumed health care trend rate - service cost and interest cost		$ 1,000,000
Effect of a 1% decrease in assumed health care trend rate - service cost and interest cost		$ 1,000,000
Individual investment, excluding funds that track to an index, percentage of total plan		5.00%
Master Trust [Member] | PRB [Member]
Defined Benefit Plans and PRB Plans [Line Items]
Defined Benefit Plan, Plan Assets, Amount		$ 144,000,000	$ 141,000,000