Employee Benefit Plans - Components of Net Periodic Benefit Income for the Pension Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Retirement Benefits [Abstract]
Service cost	$ 2,982	$ 2,390
Interest cost	20,925	24,348
Expected return on plan assets	(38,523)	(38,527)
Amortization of prior service credit	173	(17)
Amortization of actuarial loss	11,122	7,749
Net periodic benefit income	$ (3,321)	$ (4,057)