Fair Value Measurements (Financial Assets Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Thousands | Jun. 30, 2017 | Dec. 31, 2016 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | $ 66,364 | $ 80,525 |
Amortized Cost | 65,171 | 79,764 |
Cash and Cash Equivalents | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 37,855 | 33,721 |
Amortized Cost | 37,855 | 33,721 |
Cash and Cash Equivalents | Cash | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 28,754 | 32,585 |
Amortized Cost | 28,754 | 32,585 |
Cash and Cash Equivalents | Money market funds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 8,302 | 136 |
Amortized Cost | 8,302 | 136 |
Cash and Cash Equivalents | Corporate notes and bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 799 | 1,000 |
Amortized Cost | 799 | 1,000 |
Short-term Investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 24,619 | 43,331 |
Amortized Cost | 24,616 | 43,343 |
Short-term Investments | Corporate notes and bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 24,619 | 43,331 |
Amortized Cost | 24,616 | 43,343 |
Restricted cash equivalents and investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 2,700 | 2,700 |
Amortized Cost | 2,700 | 2,700 |
Related Party Transaction | Warrants issued by Rhapsody | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 1,190 | 773 |
Amortized Cost | 0 | 0 |
Level 1 | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 37,056 | 32,721 |
Level 1 | Cash and Cash Equivalents | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 37,056 | 32,721 |
Level 1 | Cash and Cash Equivalents | Cash | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 28,754 | 32,585 |
Level 1 | Cash and Cash Equivalents | Money market funds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 8,302 | 136 |
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 | 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 |
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 Transaction | Warrants issued by Rhapsody | | |
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 | 28,118 | 47,031 |
Level 2 | Cash and Cash Equivalents | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 799 | 1,000 |
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 | 799 | 1,000 |
Level 2 | Short-term Investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 24,619 | 43,331 |
Level 2 | Short-term Investments | Corporate notes and bonds | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 24,619 | 43,331 |
Level 2 | Restricted cash equivalents and investments | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | 2,700 | 2,700 |
Level 2 | Related Party Transaction | Warrants issued by Rhapsody | | |
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 | 1,190 | 773 |
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 | 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 Transaction | Warrants issued by Rhapsody | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets fair value | $ 1,190 | $ 773 |