Change in Accounting Principle (Effect on Consolidated Statement of Earnings) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 27, 2020	Jun. 28, 2020	Mar. 29, 2020	Dec. 31, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
CONSOLIDATED STATEMENTS OF EARNINGS
Operating costs and expenses	$ (9,188)	$ (8,359)	$ (8,430)	$ (7,815)	$ (9,465)	$ (8,577)	$ (8,478)	$ (8,260)	$ (33,792)	$ (34,780)	[1]	$ (31,799)	[1]
Other, net	12	24	25	21	16	20	25	31	82	92	[1]	47	[1]
As Calculated Under Previous Method
CONSOLIDATED STATEMENTS OF EARNINGS
Operating costs and expenses	(9,161)	(8,347)	(8,423)	(7,808)	(9,445)	(8,545)	(8,465)	(8,247)	(33,739)	(34,702)		(31,736)
Other, net	(15)	12	18	14	(4)	(12)	12	18	29	14		(16)
Effect of the Change in Accounting Principle | Amortization Of Actuarial Gains And Losses For U.S. Government Defined-benefit Pension Plan Participants
CONSOLIDATED STATEMENTS OF EARNINGS
Operating costs and expenses	(27)	(12)	(7)	(7)	(20)	(32)	(13)	(13)	(53)	(78)		(63)
Other, net	$ 27	$ 12	$ 7	$ 7	$ 20	$ 32	$ 13	$ 13	$ 53	$ 78		$ 63

[1] *Prior-period information has been restated for the retrospective application of a change in accounting principle related to the amortization of actuarial gains and losses for our qualified U.S. government pension plans, which we adopted in the fourth quarter of 2020. For further discussion of this change in accounting principle, see Note T to the Consolidated Financial Statements.