New Accounting Pronouncements (Details) - USD ($) $ in Millions	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset	$ 98
Operating Lease, Liability	97
Other non-current assets	592	$ 606	$ 502
Accounts Payable and Accrued Liabilities, Current	2,056	2,167	2,144
Other non-current liabilities	$ 459	437	$ 357
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset		104
Operating Lease, Liability		103
Other non-current assets		104
Accounts Payable and Accrued Liabilities, Current		23
Other non-current liabilities		$ 80