Summary of Available-For-Sale Marketable Securities (Detail) - USD ($) $ in Thousands |
Sep. 30, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Fair Market Value | $ 97,529 | $ 68,921 |
| Current Investment | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Amortized Cost | 97,492 | 68,905 |
| Gross Unrealized Gains | 38 | 29 |
| Gross Unrealized Losses | (1) | (13) |
| Fair Market Value | 97,529 | 68,921 |
| Current Investment | U.S. Treasury and government agencies | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Amortized Cost | 40,177 | 30,618 |
| Gross Unrealized Gains | 8 | 4 |
| Gross Unrealized Losses | (4) | |
| Fair Market Value | 40,185 | 30,618 |
| Current Investment | Corporate debt | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Amortized Cost | 57,315 | 38,287 |
| Gross Unrealized Gains | 30 | 25 |
| Gross Unrealized Losses | (1) | (9) |
| Fair Market Value | $ 57,344 | $ 38,303 |