Benefit Plans Schedule of Allocation of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 72	[1]	$ 65	[1]	$ 69
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1		1
Equity securities: Equity commingled funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	27		25
Debt securities: Government bonds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	36		31
Other investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 8		$ 8

[1] Fair values are determined based on valuation inputs categorized as Level 1, 2 or 3 (see Note 3. Significant Accounting Policies—Fair Value). Investment plan assets are valued using Level 1 or Level 2 inputs.