Employee Benefits - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Net periodic benefit cost
Service cost	$ 12,082	$ 10,829	$ 7,989
Interest cost	6,911	8,266	8,320
Expected return on plan assets	(16,807)	(13,539)	(10,784)
Amortization of prior service cost	(3,237)	0	0
Special event plan closure	0	0	0
Amortization of net loss	3,995	3,914	3,603
Net periodic benefit cost	2,944	9,470	9,128
Post-retirement Benefits
Net periodic benefit cost
Service cost	148	1,728	1,823
Interest cost	72	1,014	1,274
Expected return on plan assets	0	0	0
Amortization of prior service cost	(14,490)	(8,084)	(8,684)
Special event plan closure	(20,177)	0	0
Amortization of net loss	2,607	375	894
Net periodic benefit cost	$ (31,840)	$ (4,967)	$ (4,693)