Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation	$ 174,400	$ 169,705
Defined Contribution Plan, Cost	15,300	14,200	$ 9,900
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	14,444	19,308	15,614
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	16,300
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	6,609	$ 5,338	$ 6,347
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	$ 1,500
Debt Securities [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities	40.00%
Equity Securities [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Target Allocation Percentage of Assets, Equity Securities	60.00%