Fair Value Measurements (Financial Assets Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	$ 22,179	$ 38,080
Amortized Cost	22,179	37,215
Napster
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Business Combination, Contingent Consideration, Liability, Current	2,800
Business Combination, Contingent Consideration, Liability, Noncurrent	9,800
Business Combination, Contingent Consideration, Liability	12,600
Cash and Cash Equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	16,805	35,561
Amortized Cost	16,805	35,561
Cash and Cash Equivalents | Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	14,887	22,853
Amortized Cost	14,887	22,853
Cash and Cash Equivalents | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	1,918	12,708
Amortized Cost	1,918	12,708
Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		24
Amortized Cost		24
Short-term Investments | Corporate notes and bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		24
Amortized Cost		24
Restricted cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	5,374	1,630
Amortized Cost	5,374	1,630
Related Party Investment | Napster acquisition contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		865
Amortized Cost		0
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	20,305	35,561
Level 1 | Napster
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Business Combination, Contingent Consideration, Liability, Current	0
Business Combination, Contingent Consideration, Liability, Noncurrent	0
Business Combination, Contingent Consideration, Liability	0
Level 1 | Cash and Cash Equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	16,805	35,561
Level 1 | Cash and Cash Equivalents | Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	14,887	22,853
Level 1 | Cash and Cash Equivalents | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	1,918	12,708
Level 1 | Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		0
Level 1 | Short-term Investments | Corporate notes and bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		0
Level 1 | Restricted cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	3,500	0
Level 1 | Related Party Investment | Napster acquisition contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	1,874	1,654
Level 2 | Napster
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Business Combination, Contingent Consideration, Liability, Current	0
Business Combination, Contingent Consideration, Liability, Noncurrent	0
Business Combination, Contingent Consideration, Liability	0
Level 2 | Cash and Cash Equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	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 | Cash and Cash Equivalents | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Level 2 | Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		24
Level 2 | Short-term Investments | Corporate notes and bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		24
Level 2 | Restricted cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	1,874	1,630
Level 2 | Related Party Investment | Napster acquisition contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		0
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	865
Level 3 | Napster
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Business Combination, Contingent Consideration, Liability, Current	2,800
Business Combination, Contingent Consideration, Liability, Noncurrent	9,800
Business Combination, Contingent Consideration, Liability	12,600
Level 3 | Cash and Cash Equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
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 | Cash and Cash Equivalents | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Level 3 | Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		0
Level 3 | Short-term Investments | Corporate notes and bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		0
Level 3 | Restricted cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	$ 0	0
Level 3 | Related Party Investment | Napster acquisition contingent consideration
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value		$ 865