Significant Accounting Policies - Effect of Adoption of New Accounting Pronouncement, Narrative (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 24, 2018	Mar. 25, 2018	Dec. 31, 2017	Sep. 24, 2017	Jun. 25, 2017	Mar. 26, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net earnings	$ 1,253	$ 1,473	$ 1,163	$ 1,157	$ (744)	$ 963	$ 955	$ 789	$ 5,046	$ 1,963	$ 5,173
Comprehensive income									5,672	1,526	4,515
Reclassification of income tax effects from tax reform									$ 2,400
Adjustments for | ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net earnings										(39)	$ (129)
Comprehensive income										$ 38
Forecast | ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, right-of-use asset												$ 1,100