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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Retirement Benefits [Abstract]
Service cost	$ 2,395	$ 2,584	$ 7,164	$ 7,850
Interest cost	24,362	22,044	73,045	66,228
Expected return on plan assets	(38,551)	(38,470)	(115,585)	(115,574)
Amortization of prior service credit	(17)	(37)	(51)	(111)
Amortization of actuarial loss	7,752	9,920	23,247	29,814
Net periodic benefit income	$ (4,059)	$ (3,959)	$ (12,180)	$ (11,793)