Description of Business and Significant Accounting Policies Changes Due to Lease Standard Adoption (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 443		$ 0
Operating Lease, Liability, Current	93
Operating lease liabilities	355		0
Other liabilities	$ 202		$ 179
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		$ 421
Operating lease liabilities		(331)
Other Liabilities [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other liabilities		4
Accrued and Other Liabilities [Member] | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Liability, Current		$ (94)