Employee Benefit Plans - Components of Net Periodic Benefit Income for the Pension Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Retirement Benefits [Abstract]
Service cost	$ 2,925	$ 2,379	$ 5,907	$ 4,769
Interest cost	20,865	24,335	41,790	48,683
Expected return on plan assets	(38,410)	(38,507)	(76,933)	(77,034)
Amortization of prior service credit	173	(17)	346	(34)
Amortization of actuarial loss	11,088	7,746	22,210	15,495
Net periodic benefit income	$ (3,359)	$ (4,064)	$ (6,680)	$ (8,121)