New Accounting Standards (Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets
Other assets	$ 2,092	$ 2,224	$ 2,057
Stockholders’ Equity
Retained earnings	16,615	14,608	$ 14,408
Capitalized contract cost	246	219
ASU 2014-09 [Member]
Stockholders’ Equity
Capitalized contract cost	246
Deferred tax liability	59	$ 52
Balances Without Adoption of ASC 606 [Member] | ASU 2014-09 [Member]
Assets
Other assets	1,905
Stockholders’ Equity
Retained earnings	16,428
Effect of Change Higher/(Lower) [Member] | ASU 2014-09 [Member]
Assets
Other assets	187
Stockholders’ Equity
Retained earnings	$ 187