1. Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Accounts Receivable, Allowance for Credit Loss	$ 19,807	$ 19,807	$ 20,205	$ 26,700	$ 25,500
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)		1,200	(1,200)	3,900
Accounts Receivable, Allowance for Credit Loss, Writeoff		(1,600)	(6,600)	(2,700)
Accounts Receivable, Allowance for Credit Loss, Recovery		0	1,300	0
Litigation Settlement, Amount Awarded from Other Party	$ 35,300
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)		0	0	10,500
Goodwill, Impairment Loss		$ 0	$ 0	$ 282,000

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- Definition

Amount of allowance for credit loss on accounts receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
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- Definition

Amount of increase (decrease) in allowance for credit loss on accounts receivable.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

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Amount of increase in allowance for credit loss on accounts receivable, from recovery.

+ References

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Amount of direct write-downs of accounts receivable charged against the allowance.

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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.

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- Definition

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

+ References

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-Publisher FASB
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Amount awarded from other party in judgment or settlement of litigation.

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