Employee Benefit Plans - Schedule of Defined Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined benefit plans
Change in Projected Benefit Obligation
Projected benefit obligation at beginning of year	$ 654,536	$ 625,535
Interest cost	23,836	25,966	$ 27,359
Benefits paid	(33,872)	(34,997)
Actuarial (gains)/losses	(46,800)	38,032
Plan Amendments	424	0
Settlements	53,543	0
Projected benefit obligation at end of year	544,581	654,536	625,535
Plan assets:
Fair value at beginning of year	464,441	412,459
Actual return on plan assets	(32,334)	67,676
Company contributions	17,199	19,303
Benefits paid	(33,872)	(34,997)
Settlements	53,543	0
Fair value at end of year	361,891	464,441	412,459
Funded status	(182,690)	(190,095)
Amounts Recognized in Consolidated Balance Sheets:
Current liabilities	0	0
Noncurrent liabilities	(182,690)	(190,095)
Total	(182,690)	(190,095)
Amounts Recognized in Accumulated Other Comprehensive Loss:
Amounts recognized in accumulated other comprehensive loss consist of:	120,191	127,666
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	424	0
SERPs
Change in Projected Benefit Obligation
Projected benefit obligation at beginning of year	23,691	21,260
Interest cost	746	869
Benefits paid	(1,021)	(948)
Actuarial (gains)/losses	(1,034)	2,510
Plan Amendments	0	0
Settlements	5,397	0
Projected benefit obligation at end of year	16,985	23,691	21,260
Plan assets:
Fair value at beginning of year	0	0
Actual return on plan assets	0	0
Company contributions	6,418	948
Benefits paid	(1,021)	(948)
Settlements	5,397	0
Fair value at end of year	0	0	$ 0
Funded status	(16,985)	(23,691)
Amounts Recognized in Consolidated Balance Sheets:
Current liabilities	(1,231)	(6,380)
Noncurrent liabilities	(15,754)	(17,311)
Total	(16,985)	(23,691)
Amounts Recognized in Accumulated Other Comprehensive Loss:
Amounts recognized in accumulated other comprehensive loss consist of:	5,571	8,667
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax	$ 0	$ 0