Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income Loss) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Foreign currency translation adjustments (net of deferred tax asset of $15 in 2018 and deferred tax liability of $11 in 2017)	$ (1,694)	$ (1,165)
Net unrealized investment gains (net of deferred tax liability of $7 in 2017)	0	14
Net charges related to pension/post-retirement plans (net of deferred tax asset of $1,493 and $1,462 in 2018 and 2017, respectively)	(2,953)	(2,892)
Accumulated other comprehensive loss	$ (4,647)	$ (4,043)