Employee and Retiree Benefit Plans - Amounts Included in Accumulated Other Comprehensive Income Not Recognized in Net Periodic Benefit Expense (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss)	$ (269,391)
Prior service cost	(4,090)
Amounts included in accumulated other comprehensive loss which have not been recognized in net periodic benefit expense	(273,481)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss)	3,307
Prior service cost	0
Amounts included in accumulated other comprehensive loss which have not been recognized in net periodic benefit expense	$ 3,307