Postretirement Benefit Plans (Weighted-Average Asset Allocation By Investment Category) (Details)	Dec. 31, 2021	Dec. 31, 2020
Scottdale Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	100.00%	100.00%
Scottdale Defined Benefit Pension Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	12.64%	10.57%
Scottdale Defined Benefit Pension Plan [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	60.75%	58.45%
Scottdale Defined Benefit Pension Plan [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	26.61%	30.98%
Riverview Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	100.00%
Riverview Defined Benefit Plan [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	41.14%
Riverview Defined Benefit Plan [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	57.38%
Riverview Defined Benefit Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, Weighted-average asset allocation percent	1.48%