Summary of Significant Accounting Policies Contract Estimates (Details 4) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in Accounting Estimate [Line Items]
Contract with Customer, Performance Obligation Satisfied in Previous Period										$ 504	$ 538	$ 631
Operating income	$ 1,152	$ 985	$ 994	$ 934	$ 1,136	$ 951	$ 946	$ 936		4,065	3,969	3,780
Net earnings	$ 330	$ 986	$ 1,005	$ 868	$ (409)	$ 933	$ 861	$ 863		$ 3,189	$ 2,248	$ 3,229
Diluted earnings per share	$ 1.97	$ 5.89	$ 6.01	$ 5.15	$ (2.43)	$ 5.49	$ 5.06	$ 5.06		$ 19.03	$ 13.22	$ 18.49
Contracts Accounted for under Percentage of Completion [Member]
Change in Accounting Estimate [Line Items]
Operating income										$ 466	$ 480	$ 577
Net earnings										$ 368	$ 379	$ 456
Diluted earnings per share										$ 2.20	$ 2.23	$ 2.61
Aeronautics Systems | Contracts Accounted for under Percentage of Completion [Member]
Change in Accounting Estimate [Line Items]
Operating income									$ 69