Employee Benefit Plans - Components of Net Periodic Benefit Income for the Pension Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Retirement Benefits [Abstract]
Service cost	$ 3,012	$ 2,395	$ 8,919	$ 7,164
Interest cost	20,942	24,362	62,732	73,045
Expected return on plan assets	(38,550)	(38,551)	(115,483)	(115,585)
Amortization of prior service cost (credit)	173	(17)	519	(51)
Amortization of actuarial loss	11,130	7,752	33,340	23,247
Net periodic benefit income	$ (3,293)	$ (4,059)	$ (9,973)	$ (12,180)