Employee Benefit Plans and Other Postretirement Benefits (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Retirement age threshold		55 years
Postretirement benefits eligibility, years of service requirement		10 years
Period over which asset gain (losses) are amortized		5 years
Company contributions		$ 20,100,000	$ 19,000,000	$ 18,200,000
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation		1,900,000,000	2,100,000,000
Projected benefit obligations		$ 1,984,708,000	$ 2,201,021,000	$ 1,986,435,000
Expected return on plan assets		7.25%	7.25%	7.50%
Company contributions		$ 0	$ 25,000,000
Pension Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Investment in company common stock - shares		1,273,592	1,273,592
Investment in company common stock - value		$ 43,500,000	$ 64,800,000
Company contributions		$ 0
Pension Plan Assets | Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets	7.10%
Pension Plan Assets | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation		56.00%
Pension Plan Assets | Fixed Income Securities and Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation		44.00%
Postretirement Health Coverage
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations		$ 286,574,000	$ 338,488,000	$ 346,431,000
Expected return on plan assets		7.25%	7.25%	7.50%
Company contributions		$ 0	$ 15,000,000
Postretirement Health Coverage | Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets	7.25%
Postretirement Health Coverage | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation		69.00%
Postretirement Health Coverage | Fixed Income Securities and Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation		31.00%