Fair Value Measurements (Financial Assets Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	$ 33,378	$ 35,535
Accrued royalties, fulfillment and other current liabilities, Napster acquisition contingent consideration	0	4,800
Future Issuance Of Equity, Liability		2,106
Nonfinancial Liabilities Fair Value Disclosure		6,906
Cash and Cash Equivalents \| Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	28,990	23,940
Amortized Cost	28,990	23,940
Securities Investment [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	2,758	9,965
Restricted Cash Equivalents And Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	1,630	1,630
Amortized Cost	1,630	1,630
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	30,620	25,570
Future Issuance Of Equity, Liability		0
Nonfinancial Liabilities Fair Value Disclosure		0
Level 1 \| Cash and Cash Equivalents \| Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	28,990	23,940
Level 1 \| Securities Investment [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Level 1 \| Restricted Cash Equivalents And Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	1,630	1,630
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Future Issuance Of Equity, Liability		0
Nonfinancial Liabilities Fair Value Disclosure		0
Level 2 \| Cash and Cash Equivalents \| Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Level 2 \| Securities Investment [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Level 2 \| Restricted Cash Equivalents And Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	2,758	9,965
Future Issuance Of Equity, Liability		2,106
Nonfinancial Liabilities Fair Value Disclosure		6,906
Level 3 \| Cash and Cash Equivalents \| Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Level 3 \| Securities Investment [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	2,758	9,965
Level 3 \| Restricted Cash Equivalents And Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	$ 0	0
Napster
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accrued royalties, fulfillment and other current liabilities, Napster acquisition contingent consideration		4,800
Napster \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accrued royalties, fulfillment and other current liabilities, Napster acquisition contingent consideration		0
Napster \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accrued royalties, fulfillment and other current liabilities, Napster acquisition contingent consideration		0
Napster \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accrued royalties, fulfillment and other current liabilities, Napster acquisition contingent consideration		$ 4,800

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled within one year or the normal operating cycle, if longer.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

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-Publisher FASB
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-SubTopic 30
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Fair value of obligations not classified as financial liabilities. Includes, but is not limited to, accounts payable and accrued liabilities, commitments, obligations, and other liabilities.

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