Reduction in Value of Assets (Components of the Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reduction In Value Of Assets [Abstract]
Reduction in value of goodwill			$ 251,826
Reduction in value of long-lived assets	$ 26,897	$ 17,185	70,887
Total reduction in value of assets	$ 26,897	$ 17,185	$ 322,713

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
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Name:	us-gaap_GoodwillImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration