Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details 6) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018	Jan. 01, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating income	$ 943	$ 1,172	$ 817	$ 848	$ 672	$ 829	$ 864	$ 853	$ 3,780	$ 3,218	$ 3,277
Net earnings	$ 356	$ 1,244	$ 789	$ 840	$ 672	$ 750	$ 677	$ 770	$ 3,229	$ 2,869	$ 2,043
Basic earnings per share	$ 2.07	$ 7.15	$ 4.52	$ 4.82	$ 3.86	$ 4.31	$ 3.88	$ 4.41	$ 18.59	$ 16.45	$ 11.42
Diluted earnings per share	$ 2.06	$ 7.11	$ 4.50	$ 4.79	$ 3.83	$ 4.28	$ 3.86	$ 4.37	$ 18.49	$ 16.34	$ 11.32
Adjustments for New Accounting Pronouncement [Member] | Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption												$ 4
Adjustments for New Accounting Pronouncement [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption													$ 148
Operating income										$ (53)	$ (68)
Net earnings										$ (20)	$ (44)
Basic earnings per share										$ (0.11)	$ (0.25)
Diluted earnings per share										$ (0.11)	$ (0.24)