Employee Benefit Plans (Narrative) (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) employee plan	Dec. 31, 2015 USD ($) plan	Dec. 31, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of defined benefit plans | plan	4	4
Accumulated benefit obligations in excess of aggregate projected benefit obligation	$ 51,213,000	$ 47,535,000
Accumulated benefit obligations in excess of aggregate accumulated benefit obligation	51,213,000	47,535,000
Accumulated benefit obligations in excess of aggregate fair value of plan assets	0	0
401 (k) plan cost recognized	$ 1,564,000	$ 1,467,000	$ 1,219,000
Hourly Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Period for amortization of benefit plan gains and losses	14 years 2 months 4 days
Salaried Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Period for amortization of benefit plan gains and losses	14 years 3 months 21 days
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Number of defined benefit plans | plan	3
Ten-year rate of return	5.20%	6.00%	6.60%
Five-year rate of return	7.60%	6.30%	9.80%
Pension Benefits | Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of defined benefit plans | plan	2
Pension Benefits | Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of defined benefit plans | plan	1
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Age requirement for participant	60 years
Required employment period	8 years
Supplemental Employee Retirement Plan [Member] | President and Chief Executive Officer
Defined Benefit Plan Disclosure [Line Items]
Additional benefit			$ 736,000
Service period credit upon termination			36 months
Postretirement Life Insurance [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of retired employees | employee	437
Number of active employees | employee	110
Postretirement Medical [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of retired employees | employee	192
Employee contribution percentage	100.00%