Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Employee benefits plans
Defined Benefit Plan, Service Cost	$ 0	$ 0
Change in plan assets
Fair value of plan assets at beginning of year
Fair value of plan assets at end of year
Amounts recognized in consolidated balance sheets
Pensions	70,000	62,214
Net loss
Expected benefit payments	10,414
401(k) retirement plan
Expense recognized in the 401(k) retirement plan	0	400
Pension Plan
Change in benefit obligation
Benefit obligation at beginning of year	171,761	187,036
Interest cost	7,254	6,740
Actuarial (gain) loss	21,174	(12,021)
Benefits paid	(10,382)	(9,994)
Benefit obligation at end of year	189,807	171,761
Change in plan assets
Fair value of plan assets at beginning of year	107,862	126,013
Actual return on plan assets	16,742	(9,847)
Contributions	3,870	1,690
Benefits paid	(10,382)	(9,994)
Fair value of plan assets at end of year	118,092	107,862
Funded status at end of year	(71,715)	(63,899)
Amounts recognized in consolidated balance sheets
Other current liabilities	1,715	1,685
Pensions	70,000	62,214
Total	71,715	63,899
Net loss
Total	63,887	46,584
Expected benefit payments	6,400
Accumulated benefit obligation
Projected benefit obligation	189,807	171,761
Accumulated benefit obligation	189,807	171,761
Fair value of plan assets	118,092	107,862
Net Periodic Benefit Cost (Pre-Tax)
Interest cost	7,254	6,740
Expected return on plan assets	(4,446)	(6,094)
Recognized actuarial loss	2,930	2,754
Net periodic benefit cost	5,738	3,400
Amounts Recognized in Other Comprehensive (Loss) income (Pre-Tax)
Net loss	5,948	1,166
Net cost recognized in net periodic benefit cost and other comprehensive (Loss) income	11,686	$ 4,566
Estimated net loss that will be amortized from accumulated other comprehensive loss into net periodic benefit cost in next fiscal year	$ 3,600
Amortization period	19 years 8 months 12 days
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	4.35%	3.67%
Expected return on plan assets (as a percent)	4.25%	5.00%
Weighted-average assumptions used to determine benefit obligations
Discount rate (as a percent)	3.20%	4.35%
Period considered for compounded returns	15 years
Restoration Pension Plan
Net loss
Expected benefit payments	$ 1,700
Accumulated benefit obligation
Accumulated benefit obligation	$ 27,600	$ 25,300