Employee and Retiree Benefit Plans (Components of Net Periodic Benefit Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,770	$ 1,664	$ 5,306	$ 5,996
Interest cost	4,258	4,827	12,844	16,381
Expected return on plan assets	(6,038)	(5,773)	(18,326)	(18,414)
Amortization of prior service cost (credit)	155	149	467	515
Recognized actuarial loss	5,269	5,690	15,829	14,223
Net periodic benefit expense	5,414	6,557	16,120	18,701
Other - curtailment			0	586
Other - special termination benefits			0	8,435
Net periodic benefit expense			16,120	27,722
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	328	342	981	1,235
Interest cost	521	612	1,563	2,200
Expected return on plan assets	0	0	0	0
Amortization of prior service cost (credit)	0	0	0	0
Recognized actuarial loss	(8)	(24)	(23)	(24)
Net periodic benefit expense	$ 841	$ 930	2,521	3,411
Other - curtailment			0	(1,825)
Other - special termination benefits			0	0
Net periodic benefit expense			$ 2,521	$ 1,586