Benefit Plans (Narrative) (Details)	9 Months Ended
	Sep. 30, 2019 USD ($)
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer contributions	$ 51,000,000
Pension [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated additional employer contributions	10,000,000
Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer contributions	0
Postretirement [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Anticipated additional employer contributions	$ 0