Financial Instruments (Detail) - Financial Assets Measured At Fair Value On A Recurring Basis - USD ($) $ in Thousands | 6 Months Ended | |
Jun. 30, 2015 | Dec. 31, 2014 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Document Period End Date | Jun. 30, 2015 | |
Cash equivalents | $ 24,280 | $ 9,609 |
Short-term investments, amortized Cost | 270,849 | 239,621 |
Short-term investments, unrealized gains | 38 | 25 |
Short-term investments, unrealized losses | (278) | (132) |
Short-term investments, total estimated fair value | 270,609 | 239,514 |
Other Debt Obligations | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred payment obligation, amortized cost | 4,355 | |
Deferred payment obligation, unrealized gains | 705 | |
Deferred payment obligation, estimated fair value | 3,650 | |
Fair Value, Inputs, Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 7,504 | 451 |
Short-term investments, estimated fair value | 392 | 0 |
Fair Value, Inputs, Level 1 | Other Debt Obligations | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred payment obligation, estimated fair value | 0 | |
Fair Value, Inputs, Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 16,776 | 9,158 |
Short-term investments, estimated fair value | 270,217 | 239,514 |
Fair Value, Inputs, Level 2 | Other Debt Obligations | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred payment obligation, estimated fair value | 0 | |
Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Short-term investments, estimated fair value | 0 | 0 |
Fair Value, Inputs, Level 3 | Other Debt Obligations | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred payment obligation, estimated fair value | 3,650 | |
Municipal bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, amortized Cost | 150,771 | 120,270 |
Short-term investments, unrealized gains | 15 | 24 |
Short-term investments, unrealized losses | (46) | (12) |
Short-term investments, total estimated fair value | 150,740 | 120,282 |
Municipal bonds | Fair Value, Inputs, Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 0 | 0 |
Municipal bonds | Fair Value, Inputs, Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 150,740 | 120,282 |
Municipal bonds | Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 0 | 0 |
Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, amortized Cost | 7,295 | 2,498 |
Short-term investments, unrealized gains | 0 | 0 |
Short-term investments, unrealized losses | 0 | 0 |
Short-term investments, total estimated fair value | 7,295 | 2,498 |
Commercial paper | Fair Value, Inputs, Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 0 | 0 |
Commercial paper | Fair Value, Inputs, Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 7,295 | 2,498 |
Commercial paper | Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 0 | 0 |
Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, amortized Cost | 65,142 | 68,758 |
Short-term investments, unrealized gains | 3 | 1 |
Short-term investments, unrealized losses | (46) | (87) |
Short-term investments, total estimated fair value | 65,099 | 68,672 |
Corporate bonds | Fair Value, Inputs, Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 0 | 0 |
Corporate bonds | Fair Value, Inputs, Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 65,099 | 68,672 |
Corporate bonds | Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 0 | 0 |
U.S. government and agency securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, amortized Cost | 47,064 | 48,095 |
Short-term investments, unrealized gains | 20 | 0 |
Short-term investments, unrealized losses | (1) | (33) |
Short-term investments, total estimated fair value | 47,083 | 48,062 |
U.S. government and agency securities | Fair Value, Inputs, Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 0 | 0 |
U.S. government and agency securities | Fair Value, Inputs, Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 47,083 | 48,062 |
U.S. government and agency securities | Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 0 | 0 |
Equity securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, amortized Cost | 577 | |
Short-term investments, unrealized gains | 0 | |
Short-term investments, unrealized losses | (185) | |
Short-term investments, total estimated fair value | 392 | |
Equity securities | Fair Value, Inputs, Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 392 | |
Equity securities | Fair Value, Inputs, Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 0 | |
Equity securities | Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments, estimated fair value | 0 | |
Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 14,798 | 5,749 |
Commercial paper | Fair Value, Inputs, Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Commercial paper | Fair Value, Inputs, Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 14,798 | 5,749 |
Commercial paper | Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
U.S. government and agency securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | | 2,000 |
U.S. government and agency securities | Fair Value, Inputs, Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | | 0 |
U.S. government and agency securities | Fair Value, Inputs, Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | | 2,000 |
U.S. government and agency securities | Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | | 0 |
Municipal bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 1,978 | 1,409 |
Municipal bonds | Fair Value, Inputs, Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Municipal bonds | Fair Value, Inputs, Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 1,978 | 1,409 |
Municipal bonds | Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 7,504 | 451 |
Money market funds | Fair Value, Inputs, Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 7,504 | 451 |
Money market funds | Fair Value, Inputs, Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Money market funds | Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents | $ 0 | $ 0 |