Leases - Supplemental information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2019	Jan. 01, 2019
Cash paid for amounts included in the measurements of lease liabilities:
Operating cash flows from operating leases	$ (62)
ROU assets obtained in exchange for lease obligations:
Operating leases	$ 35
Supplemental balance sheet information
Balance sheet location for assets	us-gaap:OtherAssetsCurrent	us-gaap:OtherAssetsCurrent
Operating lease right-of-use assets	$ 239		$ 244
Balance sheet location for current liabilities	us-gaap:OtherLiabilitiesCurrent		us-gaap:OtherLiabilitiesCurrent
Current operating lease liabilities	$ 58		$ 53
Balance sheet location for non-current liabilities	us-gaap:OtherLiabilitiesNoncurrent		us-gaap:OtherLiabilitiesNoncurrent
Noncurrent operating lease liabilities	$ 181		$ 182