Fair Value Measurements (Financial Assets Measured at Fair Value on a Recurring Basis) (Detail) (USD $) | Jun. 30, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | $201,215 | $236,336 |
Amortized Cost | 198,391 | 229,950 |
Cash and Cash Equivalents | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 124,450 | 151,235 |
Amortized Cost | 124,451 | 151,236 |
Cash and Cash Equivalents | Cash | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 33,836 | 46,978 |
Amortized Cost | 33,836 | 46,978 |
Cash and Cash Equivalents | Money market funds | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 15,437 | 26,914 |
Amortized Cost | 15,437 | 26,914 |
Cash and Cash Equivalents | Corporate notes and bonds | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 75,177 | 77,043 |
Amortized Cost | 75,178 | 77,044 |
Cash and Cash Equivalents | U.S. government agency securities | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | ' | 300 |
Amortized Cost | ' | 300 |
Short-term Investments | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 70,583 | 74,920 |
Amortized Cost | 70,512 | 74,872 |
Short-term Investments | Corporate notes and bonds | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 57,874 | 59,766 |
Amortized Cost | 57,803 | 59,713 |
Short-term Investments | U.S. government agency securities | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 12,709 | 15,154 |
Amortized Cost | 12,709 | 15,159 |
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 | 3,182 | 7,181 |
Amortized Cost | 428 | 842 |
Level 1 | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 49,477 | 68,237 |
Level 1 | Cash and Cash Equivalents | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 33,836 | 46,979 |
Level 1 | Cash and Cash Equivalents | Cash | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 33,836 | 46,978 |
Level 1 | Cash and Cash Equivalents | Money market funds | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 0 | 1 |
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 | Cash and Cash Equivalents | U.S. government agency securities | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | ' | 0 |
Level 1 | Short-term Investments | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 12,459 | 14,077 |
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 | 12,459 | 14,077 |
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 | 3,182 | 7,181 |
Level 2 | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 151,738 | 168,099 |
Level 2 | Cash and Cash Equivalents | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 90,614 | 104,256 |
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 | 15,437 | 26,913 |
Level 2 | Cash and Cash Equivalents | Corporate notes and bonds | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 75,177 | 77,043 |
Level 2 | Cash and Cash Equivalents | U.S. government agency securities | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | ' | 300 |
Level 2 | Short-term Investments | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 58,124 | 60,843 |
Level 2 | Short-term Investments | Corporate notes and bonds | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 57,874 | 59,766 |
Level 2 | Short-term Investments | U.S. government agency securities | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 250 | 1,077 |
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 3 | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | 0 | 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 | Cash and Cash Equivalents | U.S. government agency securities | ' | ' |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ' | ' |
Financial assets fair value | ' | 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 |