Employee Benefit Plans (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015
Amounts recognized in consolidated balance sheets
Pensions	$ 62,214	$ 59,338
Net loss
Expected benefit payments	10,133
401(k) retirement plan
Expense recognized in the 401(k) retirement plan	400	3,000
Pension Plan
Change in benefit obligation
Benefit obligation at beginning of year	187,036	179,247
Interest cost	6,740	7,347
Actuarial (gain) loss	(12,021)	10,121
Benefits paid	(9,994)	(9,679)
Benefit obligation at end of year	171,761	187,036
Change in plan assets
Fair value of plan assets at beginning of year	126,013	116,725
Actual return on plan assets	(9,847)	17,292
Contributions	1,690	1,675
Benefits paid	(9,994)	(9,679)
Fair value of plan assets at end of year	107,862	126,013
Funded status at end of year	(63,899)	(61,023)
Amounts recognized in consolidated balance sheets
Other current liabilities	1,685	1,685
Pensions	62,214	59,338
Total	63,899	61,023
Net loss
Total	46,584	45,418
Expected benefit payments	2,200
Accumulated benefit obligation
Projected benefit obligation	171,761	187,036
Accumulated benefit obligation	171,761	187,036
Fair value of plan assets	107,862	126,013
Net Periodic Benefit Cost (Pre-Tax)
Interest cost	6,740	7,347
Expected return on plan assets	(6,094)	(7,328)
Recognized actuarial loss	2,754	2,754
Net periodic benefit cost	3,400	2,773
Amounts Recognized in Other Comprehensive Income (Loss) (Pre-Tax)
Net (gain) loss	1,166	(2,597)
Net cost recognized in net periodic benefit cost and other comprehensive (income) loss	4,566	$ 176
Estimated net loss that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in next fiscal year	$ 2,900
Amortization period			23 years
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	3.67%	4.21%
Expected return on plan assets (as a percent)	5.00%	6.50%
Weighted-average assumptions used to determine benefit obligations
Discount rate (as a percent)	4.35%	3.67%
Period considered for compounded returns	15 years
Restoration Pension Plan
Net loss
Expected benefit payments	$ 1,700
Accumulated benefit obligation
Accumulated benefit obligation	$ 25,300	$ 27,600