Fair Value Measurements (Financial Assets Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	$ 38,080	$ 63,364
Amortized Cost	37,215	62,375
Cash and Cash Equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	35,561	51,196
Amortized Cost	35,561	51,196
Cash and Cash Equivalents | Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	22,853	31,065
Amortized Cost	22,853	31,065
Cash and Cash Equivalents | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	12,708	20,131
Amortized Cost	12,708	20,131
Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	24	8,779
Amortized Cost	24	8,779
Short-term Investments | Corporate notes and bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	24	8,779
Amortized Cost	24	8,779
Restricted cash equivalents and investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	1,630	2,400
Restricted cash equivalents and investments | Restricted cash equivalents and investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	1,630	2,400
Related Party Investment | Warrants issued by Napster (included in Other assets)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	865	989
Amortized Cost	0	0
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	35,561	51,196
Level 1 | Cash and Cash Equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	35,561	51,196
Level 1 | Cash and Cash Equivalents | Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	22,853	31,065
Level 1 | Cash and Cash Equivalents | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	12,708	20,131
Level 1 | Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	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	0
Level 1 | Restricted cash equivalents and investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Level 1 | Related Party Investment | Warrants issued by Napster (included in Other assets)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	1,654	11,179
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	8,779
Level 2 | Short-term Investments | Corporate notes and bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	24	8,779
Level 2 | Restricted cash equivalents and investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	1,630	2,400
Level 2 | Related Party Investment | Warrants issued by Napster (included in Other assets)
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	865	989
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	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	0
Level 3 | Restricted cash equivalents and investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	0	0
Level 3 | Related Party Investment | Warrants issued by Napster (included in Other assets)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	$ 865	$ 989