Employee Benefit Plans (Summary of Pension and Postretirement Plan Asset Allocation) (Details)	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	100.00%	100.00%
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	100.00%	100.00%
U.S. Equities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	3.00%	4.00%
U.S. Equities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	50.00%	43.00%
International Equities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	5.00%	5.00%
International Equities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	11.00%	10.00%
Fixed Maturities | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	64.00%	63.00%
Fixed Maturities | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	29.00%	37.00%
Short-term investments | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	1.00%	0.00%
Short-term investments | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	10.00%	10.00%
Real Estate | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	11.00%	10.00%
Real Estate | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	0.00%	0.00%
Other | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	16.00%	18.00%
Other | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset class to total plan assets (actual)	0.00%	0.00%