Employee Benefit Plans and Other Postretirement Benefits - Components Of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension and SERPA Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 25,408	$ 32,340	$ 31,584
Interest cost	85,483	82,778	85,076
Expected return on plan assets	(142,323)	(147,671)	(141,385)
Prior service (credit) cost	(1,930)	(420)	1,018
Net loss	44,511	64,773	43,993
Special early retirement benefits	1,583	0	0
Curtailment loss (gain)	0	1,017	0
Settlement loss	1,503	0	0
Net periodic benefit cost	14,235	32,817	20,286
Postretirement Health Coverage
Defined Benefit Plan Disclosure [Line Items]
Service cost	4,449	7,180	7,500
Interest cost	11,753	11,556	13,648
Expected return on plan assets	(14,030)	(14,161)	(12,623)
Prior service (credit) cost	(2,381)	(1,842)	(2,171)
Net loss	277	1,817	3,261
Special early retirement benefits	0	0	0
Curtailment loss (gain)	(960)	(886)	0
Settlement loss	0	0	0
Net periodic benefit cost	$ (892)	$ 3,664	$ 9,615