Basis Of Presentation (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basis of Presentation [Line Items]
Net earnings		$ 2,477	$ 1,579
Increase/(Decrease) in revenue due to change in accounting estimate		117	207
Increase/(Decrease) in Earnings from operations due to change in accounting estimate		$ 78	$ 108
Change in Earnings Per Share Due to Change in Accounting Estimate		$ 0.11	$ 0.13
Retained earnings		$ 52,095		$ 49,618
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]	(16,162)	$ (13,415)	(16,373)	$ (13,623)
Accounting Standards Update 2014-09 [Member]
Basis of Presentation [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption				1,301	139	$ 901
Net earnings				261	$ 139
Adjustments for New Accounting Pronouncement [Member]
Basis of Presentation [Line Items]
Net earnings			128
Retained earnings				4,298
Accumulated Other Comprehensive Income (Loss), Net of Tax				(2,997)
Accounting Standards Update 2018-02 [Member]
Basis of Presentation [Line Items]
Retained earnings				2,997
Accumulated Other Comprehensive Income (Loss), Net of Tax				(2,997)
Retained Earnings [Member]
Basis of Presentation [Line Items]
Net earnings		$ 2,477	$ 1,579
Retained Earnings [Member] | Accounting Standards Update 2014-09 [Member]
Basis of Presentation [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 1,301		$ 901

[1] Net of tax.