2018 Business Combinations (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 681,349	$ 640,203	$ 664,922	$ 631,791
Measurement Period Adjustments [Abstract]
Goodwill	(6,669)	$ 0	0
2018 Acquisitions [Member]
Business Acquisition [Line Items]
Receivables, net	18,984		18,984
Inventories	10,101		10,329
Prepayments and other current assets	501		515
Total current assets	29,586		29,828
Property, plant and equipment	138,435		131,766
Goodwill	26,462		33,131
Other Intangible assets, net	8,227		8,227
Other	927		927
Total deferred charges and other assets	35,616		42,285
Total assets acquired	203,637		203,879
Current liabilities	10,880		11,122
Asset retirement obligation	914		914
Deferred income taxes	5,565		5,565
Total deferred credits and other liabilities	6,479		6,479
Total liabilities assumed	17,359		17,601
Total consideration (fair value)	186,278		$ 186,278
Measurement Period Adjustments [Abstract]
Receivables, net	(228)
Inventories	(14)
Prepayments and other current assets	(242)
Property, plant and equipment	6,669
Goodwill	(6,669)
Total deferred charges and other assets	(6,669)
Total assets acquired	(242)
Current liabilities	(242)
Total liabilities assumed	$ (242)