Accounts Receivable (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable [Line Items]
Total accounts receivable	$ 3,161	$ 3,544	[1]
Non-U.S. Government
Accounts Receivable [Line Items]
Total accounts receivable	1,701	1,847
Receivables related to long-term production programs	1,600	1,700
Receivables related to long-term production programs, net of customer advances	(245)	(295)
U.S. Government
Accounts Receivable [Line Items]
Total accounts receivable	1,040	1,076
Commercial
Accounts Receivable [Line Items]
Total accounts receivable	$ 420	$ 621

[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.