|
Summary of Significant Accounting Policies - Summary of Contractual Underlying Maturities of Short-Term Investments (Detail) (USD $)
In Thousands, unless otherwise specified
|
Mar. 31, 2015
|
Dec. 31, 2014
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term Investments, Less than 1 Year |
$ 381,596 |
$ 355,164 |
| Short-term Investments, 1 to 3 Years |
191,213 |
165,680 |
| Short-term Investments, fair value |
572,809 |
520,844 |
| Time Deposits [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term Investments, Less than 1 Year |
25,321 |
21,479 |
| Short-term Investments, 1 to 3 Years |
6,460 |
247 |
| Short-term Investments, fair value |
31,781 |
21,726 |
| Commercial paper [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term Investments, Less than 1 Year |
|
3,999 |
| Short-term Investments, fair value |
|
3,999 |
| U.S. government agency bonds [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term Investments, 1 to 3 Years |
15,427 |
|
| Short-term Investments, fair value |
15,427 |
|
| Corporate bonds [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term Investments, Less than 1 Year |
229,616 |
240,570 |
| Short-term Investments, 1 to 3 Years |
118,308 |
112,642 |
| Short-term Investments, fair value |
347,924 |
353,212 |
| International government bonds [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term Investments, Less than 1 Year |
2,709 |
1,501 |
| Short-term Investments, fair value |
2,709 |
1,501 |
| Municipal bonds [Member] |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Short-term Investments, Less than 1 Year |
123,950 |
87,615 |
| Short-term Investments, 1 to 3 Years |
51,018 |
52,791 |
| Short-term Investments, fair value |
$ 174,968 |
$ 140,406 |