Employee Benefit Plans (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans
Estimated net loss and prior service cost that will be amortized from accumulated other comprehensive income into net periodic cost over the next year
Estimated net loss that will be amortized from accumulated other comprehensive income into net periodic cost over the next year	$ 1,400,000
Prior service credit that will be amortized from accumulated other comprehensive income into net periodic cost over the next year	(2,300,000)
Change in benefit obligation:
Benefit obligation at beginning of year	129,802,000	131,927,000
Service cost	4,551,000	7,431,000	5,713,000
Interest cost	5,203,000	5,729,000	5,452,000
Amendments	(14,000)	(26,919,000)
Actuarial (gain)/ loss	(14,422,000)	14,527,000
Benefits paid	(3,353,000)	(2,893,000)
Benefit obligation at end of year	121,767,000	129,802,000	131,927,000
Change in plan assets:
Fair value of plan assets at beginning of year	115,489,000	105,159,000
Actual return on plan assets	18,020,000	8,393,000
Employer contributions	335,000	4,830,000
Benefits paid	(3,353,000)	(2,893,000)
Fair value of plan assets at end of period	130,491,000	115,489,000	105,159,000
Funded status at end of year	8,724,000	(14,313,000)
Additional information
Benefits as a percentage of career average pay for each year	1.00%
Number of hours of service need to be completed to avail additional benefit under amendment	1000 hours
Employee age required to participate in the plan	70 years 6 months
Assumptions used to develop the net periodic pension cost
Discount rate (as a percent)	4.06%	4.39%	5.57%
Expected long-term rate of return on assets (as a percent)	7.50%	7.50%	7.50%
Rate of increase in compensation levels (as a percent)	3.00%	3.00%	3.00%
Assumptions used to determine benefit obligations
Discount rate (as a percent)	4.86%	4.06%	4.39%
Expected long-term rate of return on assets (as a percent)	7.50%	7.50%	7.50%
Rate of increase in compensation levels (as a percent)	3.00%	3.00%	3.00%
Postretirement Healthcare Plan
Estimated net loss and prior service cost that will be amortized from accumulated other comprehensive income into net periodic cost over the next year
Estimated net loss that will be amortized from accumulated other comprehensive income into net periodic cost over the next year	53,000	50,000	52,000
Change in benefit obligation:
Benefit obligation at beginning of year	1,620,000	1,588,000
Interest cost	63,000	66,000	86,000
Actuarial (gain)/ loss	(83,000)	114,000
Benefits paid	(175,000)	(148,000)
Benefit obligation at end of year	1,425,000	1,620,000	1,588,000
Change in plan assets:
Employer contributions	176,000	148,000
Benefits paid	(175,000)	(148,000)
Funded status at end of year	(1,425,000)	(1,620,000)
Assumptions used to develop the net periodic pension cost
Discount rate (as a percent)	4.06%	4.39%	5.57%
Monthly cost of healthcare insurance per beneficiary	$ 351	$ 327	$ 320
Annual rate of increase in healthcare costs (as a percent)	4.00%	4.00%	4.00%