Employee Benefit Plans (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amounts recognized in consolidated balance sheets
Pensions	$ 60,836	$ 55,491
401(k) retirement plan
Expense recognized in the 401(k) retirement plan	3,000	3,000	$ 3,000
Pension Plan
Change in benefit obligation
Benefit obligation at beginning of year	178,715	191,065
Interest cost	7,802	7,724	7,698
Actuarial (gain) loss	2,127	(10,861)
Benefits paid	(9,397)	(9,213)
Benefit obligation at end of year	179,247	178,715	191,065
Change in plan assets
Fair value of plan assets at beginning of year	121,682	124,372
Actual return on plan assets	2,883	982
Contributions	1,557	5,541
Benefits paid	(9,397)	(9,213)
Fair value of plan assets at end of year	116,725	121,682	124,372
Funded status at end of year	(62,522)	(57,033)
Amounts recognized in consolidated balance sheets
Other current liabilities	1,686	1,542
Pensions	60,836	55,491
Total	62,522	57,033
Amounts recognized in accumulated other comprehensive income (loss)
Total	46,977	43,915
Accumulated benefit obligation
Projected benefit obligation	179,247	178,715
Accumulated benefit obligation	179,247	178,715
Fair value of plan assets	116,725	121,682
Net Periodic Benefit Cost (Pre-Tax)
Service cost	0	0	100
Interest cost	7,802	7,724	7,698
Expected return on plan assets	(8,245)	(8,637)	(8,418)
Recognized actuarial loss	2,386	6,228	3,654
Net periodic benefit cost	1,943	5,315	3,034
Amounts Recognized in Other Comprehensive Income (Loss) (Pre-Tax)
Net (gain) loss	5,103	(9,408)	28,802
Net (benefit) cost recognized in net periodic benefit cost and other comprehensive (income) loss	7,046	$ (4,093)	$ 31,836
Estimated net loss that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in next fiscal year	$ 2,700
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	4.49%	4.13%	4.94%
Expected return on plan assets (as a percent)	7.00%	7.00%	7.00%
Weighted-average assumptions used to determine benefit obligations
Discount rate (as a percent)	4.21%	4.49%
Period considered for compounded returns	15 years
Pension Plan | Scenario, previously reported
Weighted-average assumptions used to determine benefit obligations
Amortization period	9 years
Pension Plan | Scenario, Adjustment
Weighted-average assumptions used to determine benefit obligations
Amortization period	23 years
Restoration Pension Plan
Accumulated benefit obligation
Accumulated benefit obligation	$ 26,600	$ 26,400