Employee Benefit Plans (Asset Allocations) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	$ 155	$ 143	$ 162
Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	5	5
Significant Observable Inputs (Level 2)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	142	132
Significant Unobservable Inputs (Level 3)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Net Asset Value (NAV)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	8	6
Cash and money market
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	5	5
Cash and money market | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	5	5
Cash and money market | Significant Observable Inputs (Level 2)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Cash and money market | Significant Unobservable Inputs (Level 3)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Cash and money market | Net Asset Value (NAV)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Equity securities
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	59	52
Equity securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Equity securities | Significant Observable Inputs (Level 2)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	59	52
Equity securities | Significant Unobservable Inputs (Level 3)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Equity securities | Net Asset Value (NAV)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Fixed income securities
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	77	73
Fixed income securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Fixed income securities | Significant Observable Inputs (Level 2)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	77	73
Fixed income securities | Significant Unobservable Inputs (Level 3)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Fixed income securities | Net Asset Value (NAV)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Global real estate fund
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	6	7
Global real estate fund | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Global real estate fund | Significant Observable Inputs (Level 2)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	6	7
Global real estate fund | Significant Unobservable Inputs (Level 3)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Global real estate fund | Net Asset Value (NAV)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Domestic private equity
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	8	6
Domestic private equity | Quoted Prices in Active Markets for Identical Assets (Level 1)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Domestic private equity | Significant Observable Inputs (Level 2)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Domestic private equity | Significant Unobservable Inputs (Level 3)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	0	0
Domestic private equity | Net Asset Value (NAV)
Schedule Of Pension And Other Postretirement Benefits Expected Benefit Payments [Line Items]
Fair value of plan assets	$ 8	$ 6