Supplemental Cash Flow Information (Schedule of Supplemental Cash Flow) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Supplemental Cash Flow Information
Interest paid, net of interest capitalized	$ 34,955	$ 36,278
Interest received	2,491	2,009
Net income taxes paid	23,193	7,902
Non-cash purchase of property, plant and equipment under capital lease	$ 10,747	$ 5,490