Leases - Supplemental information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019
Cash paid for amounts included in the measurements of lease liabilities:
Operating cash flows from operating leases	$ (16)
ROU assets obtained in exchange for lease obligations:
Operating leases	$ 10
Supplemental balance sheet information
Balance sheet location for assets	us-gaap:OtherAssetsMember	us-gaap:OtherAssetsMember
Operating lease right-of-use assets	$ 236	$ 244
Balance sheet location for current liabilities	us-gaap:OtherCurrentLiabilitiesMember	us-gaap:OtherCurrentLiabilitiesMember
Current operating lease liabilities	$ 54	$ 53
Balance sheet location for non-current liabilities	us-gaap:OtherLiabilitiesMember	us-gaap:OtherNoncurrentLiabilitiesMember
Noncurrent operating lease liabilities	$ 181	$ 182