Fair Value Measurements (Financial Assets Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Thousands | Sep. 30, 2015 | Dec. 31, 2014 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | $ 118,077 | $ 167,382 |
Amortized Cost | 115,615 | 165,121 |
Cash and Cash Equivalents | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 61,831 | 103,253 |
Amortized Cost | 61,831 | 103,255 |
Cash and Cash Equivalents | Cash | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 36,321 | 30,105 |
Amortized Cost | 36,321 | 30,105 |
Cash and Cash Equivalents | Money market funds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 1,064 | 11,629 |
Amortized Cost | 1,064 | 11,630 |
Cash and Cash Equivalents | Corporate notes and bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 24,446 | 61,519 |
Amortized Cost | 24,446 | 61,520 |
Short-term Investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 50,412 | 58,453 |
Amortized Cost | 50,422 | 58,438 |
Short-term Investments | Corporate notes and bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 49,812 | 51,453 |
Amortized Cost | 49,822 | 51,438 |
Short-term Investments | U.S. government agency securities | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 600 | 7,000 |
Amortized Cost | 600 | 7,000 |
Restricted cash equivalents and investments | Restricted cash equivalents and investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 3,000 | 3,000 |
Amortized Cost | 3,000 | 3,000 |
Equity Investment in Publicly Traded Securities | Publicly Traded Investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 1,756 | 2,676 |
Amortized Cost | 362 | 428 |
Related Party Transaction [Domain] | Warrants issued by Rhapsody | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 1,078 | |
Amortized Cost | 0 | |
Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 39,741 | 51,410 |
Level 1 | Cash and Cash Equivalents | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 37,385 | 41,734 |
Level 1 | Cash and Cash Equivalents | Cash | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 36,321 | 30,105 |
Level 1 | Cash and Cash Equivalents | Money market funds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 1,064 | 11,629 |
Level 1 | Cash and Cash Equivalents | Corporate notes and bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 0 | 0 |
Level 1 | Short-term Investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 600 | 7,000 |
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 | Short-term Investments | U.S. government agency securities | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 600 | 7,000 |
Level 1 | Restricted cash equivalents and investments | Restricted cash equivalents and investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 0 | 0 |
Level 1 | Equity Investment in Publicly Traded Securities | Publicly Traded Investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 1,756 | 2,676 |
Level 1 | Related Party Transaction [Domain] | Warrants issued by Rhapsody | | |
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 | 77,258 | 115,972 |
Level 2 | Cash and Cash Equivalents | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 24,446 | 61,519 |
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 | Cash and Cash Equivalents | Corporate notes and bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 24,446 | 61,519 |
Level 2 | Short-term Investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 49,812 | 51,453 |
Level 2 | Short-term Investments | Corporate notes and bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 49,812 | 51,453 |
Level 2 | Short-term Investments | U.S. government agency securities | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 0 | 0 |
Level 2 | Restricted cash equivalents and investments | Restricted cash equivalents and investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 3,000 | 3,000 |
Level 2 | Equity Investment in Publicly Traded Securities | Publicly Traded Investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 0 | 0 |
Level 2 | Related Party Transaction [Domain] | Warrants issued by Rhapsody | | |
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 | 1,078 | 0 |
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 | Cash and Cash Equivalents | Corporate notes and bonds | | |
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 | Short-term Investments | U.S. government agency securities | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 0 | 0 |
Level 3 | Restricted cash equivalents and investments | Restricted cash equivalents and investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 0 | 0 |
Level 3 | Equity Investment in Publicly Traded Securities | Publicly Traded Investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 0 | $ 0 |
Level 3 | Related Party Transaction [Domain] | Warrants issued by Rhapsody | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | $ 1,078 | |