Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Accumulated Benefit Obligation	$ 158,580	$ 140,442
Defined Benefit Plan, Amortization of Net Gains (Losses)	4,100
Defined Benefit Plan, Amortization of Net Prior Service Cost (Credit)	800
Defined Contribution Plan, Cost Recognized	9,900	9,000	$ 7,800
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost	15,614	13,098	10,710
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	15,100
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost	6,347	$ 9,099	$ 5,376
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	$ 5,100
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%