Pension and Other Post-Retirement Benefits - Components of Pension Expense and Other Postretirement Benefit Expense (Details) - Pension Plans, Defined Benefit - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plans Disclosure [Line Items]
Interest cost	$ 3,275	$ 4,449
Expected return on plan assets	(5,574)	(4,964)
Amortization of actuarial loss	2,849	2,484
Total	$ 550	$ 1,969