Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment		$ 1,806,603	$ 1,696,729
Less: Accumulated depreciation		(1,244,817)	(1,263,936)
Property, plant and equipment, net		561,786	432,793	$ 444,683
Land
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment		30,409	10,143
Land improvements
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment		19,155	15,961
Land improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Land improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	20 years
Buildings and improvements
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment		182,795	163,037
Buildings and improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Buildings and improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	40 years
Machinery and equipment
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment		1,518,652	1,470,620
Machinery and equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	3 years
Machinery and equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	20 years
Uncompleted construction
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment		$ 55,592	$ 36,968