Acquisitions (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 664,922	$ 631,791	$ 631,791
2018 Acquisitions [Member]
Business Acquisition [Line Items]
Receivables, net	18,984
Inventories	10,329
Other current assets	515
Total current assets	29,828
Property, plant and equipment	131,766
Goodwill	33,131
Other intangible assets, net	8,227
Other	927
Total deferred charges and other assets	42,285
Total assets acquired	203,879
Current liabilities	11,122
Asset retirement obligation	914
Deferred income taxes	5,565
Total deferred credits and other liabilities	6,479
Total liabilities assumed	17,601
Total consideration (fair value)	$ 186,278