Accounting Pronouncements - Leases (Details) - USD ($) $ in Millions	Jan. 01, 2019	Dec. 31, 2019	Jan. 31, 2019	Dec. 31, 2018
Assets [Abstract]
Other current assets	$ 139	$ 181		$ 146
Operating lease right-of-use assets	244	$ 239
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]		Other current assets	Other current assets
Other assets	1,384
Liabilities [Abstract]
Other current liabilities	489	$ 676		492
Current operating lease liabilities	$ 53	$ 58
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other current liabilities	Other current liabilities
Other liabilities	$ 273	$ 380		287
Noncurrent operating lease liabilities	$ 182	$ 181
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other liabilities	Other liabilities
Effect of Tax Cuts and Jobs Act [Abstract]
Reclassification of stranded tax effects	$ 79
As Previously reported
Assets [Abstract]
Other current assets				140
Other assets				1,409
Liabilities [Abstract]
Other current liabilities				492
Other liabilities				$ 287
ASU 2016-02
Lessee Disclosure [Abstract]
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected [Fixed List]	Modified Retrospective
New Accounting Pronouncement or Change in Accounting Principle, Prior Period Not Restated [true false]	true
Practical expedient package adopted	true
Land easement practical expedient	true
Impact on opening retained earnings balance	$ 0
ASU 2016-02 | Adjustments Due to Adoption
Assets [Abstract]
Other current assets	(1)
Operating lease right-of-use assets	244
Other assets	(25)
Liabilities [Abstract]
Other current liabilities	(3)
Current operating lease liabilities	53
Other liabilities	(14)
Noncurrent operating lease liabilities	$ 182