LEASES - 2019 Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Leases [Abstract]
Operating right-of-use lease assets included within other long-term assets	$ 416
Operating right-of-use lease liabilities included within trade accounts payable and accrued expenses	122
Operating right-of-use lease liabilities included within other long-term liabilities	328
Fixed operating lease costs	39
Variable lease costs	16
Sublease rental income	$ 9
Weighted average remaining lease term (in years)	4 years 9 months
Weighted average discount rate (percent)	4.30%
Operating lease cash payments	$ 39