Summary of Significant Accounting Policies (Cumulative Effect of Changes for Adoption of New Revenue Guidance) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 204
Accrued liabilities	2
Other non-current liabilities	$ 11
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		$ 220
Accrued liabilities		5
Other non-current liabilities		$ 24