Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Amounts recognized in consolidated balance sheets
Other current liabilities		$ 1,542	$ 1,537
Pensions		55,491	65,156
Total		57,033	66,693
Amounts recognized in accumulated other comprehensive income (loss)
Net loss		43,915	49,560
Prior service cost		0	0
Total		43,915	49,560
Supplemental Employee Retirement Plan
Employee Benefits Plans
Reduction of plan expense over the remainder of 2014			400
Curtailments			(1,100)
Expected benefit payments in next fiscal year		1,500
Change in benefit obligation
Curtailments			(1,100)
Accumulated benefit obligation in excess of plan assets
Accumulated benefit obligation		26,400	28,200
Pension Plan
Employee Benefits Plans
Curtailments		0	(1,070)
Expected benefit payments in next fiscal year		9,418
Change in benefit obligation
Benefit obligation at beginning of year	$ 178,715	191,065	161,370
Service cost		0	100	$ 343
Interest cost		7,724	7,698	7,237
Actuarial (gain) loss		(10,861)	32,018
Benefits paid		(9,213)	(9,051)
Curtailments		0	(1,070)
Benefit obligation at end of year		178,715	191,065	161,370
Change in plan assets
Fair value of plan assets at beginning of year	$ 121,682	124,372	120,604
Actual return on plan assets		982	6,887
Contributions		5,541	5,932
Benefits paid		(9,213)	(9,051)
Fair value of plan assets at end of year		121,682	124,372	120,604
Funded status at end of year		(57,033)	(66,693)
Accumulated benefit obligation in excess of plan assets
Projected benefit obligation		178,715	191,065
Accumulated benefit obligation		178,715	191,065
Fair value of plan assets		121,682	124,372
Net Periodic Benefit Cost (Pre-Tax)
Service cost		0	100	343
Interest cost		7,724	7,698	7,237
Expected return on plan assets		(8,637)	(8,418)	(7,383)
Recognized actuarial loss		6,228	3,654	6,687
Net periodic benefit cost		5,315	3,034	6,884
Amounts Recognized in Other Comprehensive Income (Loss) (Pre-Tax)
Net (gain) loss		(9,408)	28,802	(36,920)
Total (benefit) cost recognized in other comprehensive loss		(9,408)	28,802	(36,920)
Net (benefit) cost recognized in net periodic benefit cost and other comprehensive (income) loss		(4,093)	$ 31,836	$ (30,036)
Estimated net loss that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in next fiscal year		$ 2,300
Previous amortization period		9 years
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)		4.13%	4.94%	4.15%
Expected return on plan assets (as a percent)		7.00%	7.00%	7.25%
Rate of compensation increase (as a percent)				3.00%
Weighted-average assumptions used to determine benefit obligations
Discount rate (as a percent)		4.49%	4.13%
Period considered for compounded returns		15 years
Scenario, Forecast | Pension Plan
Amounts Recognized in Other Comprehensive Income (Loss) (Pre-Tax)
Previous amortization period	24 years