Pension and Other Postretirement Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Time horizon	20 years
Investment in company stock	$ 0	$ 0
Plan assets	$ 668,481,000	578,347,000
United States Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	23.50%
Non U.S. Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	15.00%
Global Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	6.50%
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation	55.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Settlement expense	$ 0	0	$ 10,153,000
Plan assets	668,481,000	578,347,000	679,245,000
Expected benefit payments in 2020	44,619,000
Pension Benefits | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments in 2020	1,687,000
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Settlement expense	0	0	0
Plan assets	0	$ 0	$ 0
Expected benefit payments in 2020	$ 31,833,000