Employee Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed	5.70%
Ultimate trend rate	4.50%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations (percent)	27.00%
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations (percent)	73.00%
Defined benefit pension plan
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation of pension plans	$ 202,300,000	$ 217,500,000
Weighted-average interest credit rate (as percent)	4.25%	4.25%
Discount rate increased plan obligations	$ 19,000,000.0
Pension contributions planned for next fiscal year	0
Other postretirement benefits payments	17,100,000	$ 17,500,000	$ 17,900,000
Other postretirement benefits plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate increased plan obligations	8,400,000
Health care cost trend assumption	6,000,000.0
Claims cost assumption	$ 5,100,000