Reduction in Value of Assets (Components of the Expense) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reduction In Value Of Assets [Abstract]
Reduction in value of goodwill				$ 668,838		$ 330,500
Reduction in value of long-lived assets				70,887	$ 14,155	143,803
Retirments of long-lived assets						26,102
Total reduction in value of assets	$ 739,725	$ 4,202	$ 9,953	$ 739,725	$ 14,155	$ 500,405

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Name:	us-gaap_GoodwillImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration