Pension and Other Postretirement Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Time horizon	20 years
Investment in company stock	$ 0	$ 0
Plan assets	$ 578,347,000	679,245,000
United States Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (as a percent)	26.00%
Non U.S. Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (as a percent)	16.50%
Global Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (as a percent)	7.50%
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation (as a percent)	50.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Settlement expense	$ 0	10,153,000	$ 22,196,000
Plan assets	578,347,000	679,245,000	632,434,000
Expected benefit payments in 2018	43,588,000
Pension Benefits | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Expected benefit payments in 2018	1,623,000
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Settlement expense	0	0	0
Plan amendments			28,164,000
Plan assets	0	$ 0	$ 0
Expected benefit payments in 2018	$ 32,345,000