Employee Benefit Plans - Amounts Recognized in Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Non-current liabilities	$ (236,625)	$ (233,658)
Pension
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	37,505	30,395
Current liabilities	(3,745)	(3,773)
Non-current liabilities	(196,275)	(195,575)
Net amount recognized	(162,515)	(168,953)
Postretirement
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	0	0
Current liabilities	(2,221)	(3,160)
Non-current liabilities	(40,350)	(38,083)
Net amount recognized	$ (42,571)	$ (41,243)