Employee Benefit Plans (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) employees plans yr	Dec. 31, 2014 USD ($) plans	Dec. 31, 2013 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of defined benefit plans | plans	4	4
Accumulated other comprehensive income (loss)	$ 34,319	$ 29,899	$ 26,216
Accumulated benefit obligations in excess of aggregate projected benefit obligation	47,535	41,214
Accumulated benefit obligations in excess of aggregate accumulated benefit obligation	47,535	41,214
Accumulated benefit obligations in excess of aggregate fair value of plan assets	0	0
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
Defined Contribution Plan, Cost Recognized	$ 1,467	1,219	1,190
Qualified Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of defined benefit plans | plans	2
Non-qualified Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of defined benefit plans | plans	1
Supplemental Employee Retirement Plans [Member]
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
2016	$ 0
2017	0
2018	0
2019	0
2020	7,111
2021 - 2025	$ 47,586
Postretirement Medical [Member]
Defined Benefit Plan Disclosure [Line Items]
Number Of Participating Employees | employees	219
Employee Contribution Percentage	100.00%
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
2016	$ 595
2017	618
2018	607
2019	609
2020	606
2021 - 2025	$ 2,953
Life Insurance Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Number Of Participating Employees | employees	164
Postretirement Life Insurance [Member]
Defined Benefit Plan Disclosure [Line Items]
Number Of Participating Employees | employees	402
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of defined benefit plans | plans	3
Accumulated other comprehensive income (loss)	$ 35,258	30,481	27,102
Defined Benefit Plan, Estimated Future Benefit Payments [Abstract]
2016	9,548
2017	9,053
2018	8,618
2019	8,139
2020	14,786
2021 - 2025	79,462
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated other comprehensive income (loss)	$ (939)	$ (582)	$ (886)
Houly Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Period For Amortization of Benefit Plan Gains and Losses (in years)	16 years 1 month 28 days
Salaried Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Period For Amortization of Benefit Plan Gains and Losses (in years)	15 years 11 months 26 days
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of Excess in Projected Benefit Obligation and Fair Value Assets To Be Amortized	10.00%
Minimum [Member] | Supplemental Employee Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Age Requirement For Plant Participation | yr	60
Required employment period	8 years
Ten Year Rate of Return [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual Rate of Return Period (in years)	10 years
Actual Rate of Return On Plan Assets	6.00%	6.60%	7.20%
Five Year Rate of Return [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual Rate of Return Period (in years)	5 years
Actual Rate of Return On Plan Assets	6.30%	9.80%	13.60%
President and Chief Executive Officer [Member] | Supplemental Employee Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Additional SERP Benefit			$ 736
Service Period Credit Upon Termination			36 months