Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified
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Sep. 30, 2014
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Dec. 31, 2013
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
$ 649,037 |
$ 523,607 |
Commercial Paper [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
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Investments |
20,488 |
124,319 |
Corporate notes and bonds [Member]
|
|
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
548,370 |
399,288 |
Certificates of Deposit [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
20,099 |
|
US Government Agencies Debt Securities [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
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Investments |
60,080 |
|
Level 1 [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
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Total |
191,251 |
104,581 |
Level 2 [Member]
|
|
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Total |
692,872 |
785,329 |
Total [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Total |
884,123 |
889,910 |
Cash [Member] | Level 1 [Member]
|
|
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Cash and cash equivalents |
110,110 |
69,333 |
Cash [Member] | Level 2 [Member]
|
|
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Cash and cash equivalents |
0 |
0 |
Cash [Member] | Total [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Cash and cash equivalents |
110,110 |
69,333 |
Cash Equivalents [Member] | Level 1 [Member] | Money Market Funds [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Cash and cash equivalents |
81,141 |
35,248 |
Cash Equivalents [Member] | Level 1 [Member] | Commercial Paper [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Cash and cash equivalents |
0 |
0 |
Cash Equivalents [Member] | Level 2 [Member] | Money Market Funds [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Cash and cash equivalents |
0 |
0 |
Cash Equivalents [Member] | Level 2 [Member] | Commercial Paper [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Cash and cash equivalents |
43,835 |
261,722 |
Cash Equivalents [Member] | Total [Member] | Money Market Funds [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Cash and cash equivalents |
81,141 |
35,248 |
Cash Equivalents [Member] | Total [Member] | Commercial Paper [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Cash and cash equivalents |
43,835 |
261,722 |
Short-term Investments [Member] | Level 1 [Member] | Commercial Paper [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
0 |
0 |
Short-term Investments [Member] | Level 1 [Member] | Corporate notes and bonds [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
0 |
0 |
Short-term Investments [Member] | Level 1 [Member] | Certificates of Deposit [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
0 |
|
Short-term Investments [Member] | Level 1 [Member] | US Government Agencies Debt Securities [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
0 |
|
Short-term Investments [Member] | Level 2 [Member] | Commercial Paper [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
20,488 |
124,319 |
Short-term Investments [Member] | Level 2 [Member] | Corporate notes and bonds [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
359,875 |
143,932 |
Short-term Investments [Member] | Level 2 [Member] | Certificates of Deposit [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
16,604 |
|
Short-term Investments [Member] | Level 2 [Member] | US Government Agencies Debt Securities [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
14,019 |
|
Short-term Investments [Member] | Total [Member] | Commercial Paper [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
20,488 |
124,319 |
Short-term Investments [Member] | Total [Member] | Corporate notes and bonds [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
359,875 |
143,932 |
Short-term Investments [Member] | Total [Member] | Certificates of Deposit [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
16,604 |
|
Short-term Investments [Member] | Total [Member] | US Government Agencies Debt Securities [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
14,019 |
|
Other Long-term Investments [Member] | Level 1 [Member] | Corporate notes and bonds [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
0 |
0 |
Other Long-term Investments [Member] | Level 1 [Member] | Certificates of Deposit [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
0 |
|
Other Long-term Investments [Member] | Level 1 [Member] | US Government Agencies Debt Securities [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
0 |
|
Other Long-term Investments [Member] | Level 2 [Member] | Corporate notes and bonds [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
188,495 |
255,356 |
Other Long-term Investments [Member] | Level 2 [Member] | Certificates of Deposit [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
3,495 |
|
Other Long-term Investments [Member] | Level 2 [Member] | US Government Agencies Debt Securities [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
46,061 |
|
Other Long-term Investments [Member] | Total [Member] | Corporate notes and bonds [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
188,495 |
255,356 |
Other Long-term Investments [Member] | Total [Member] | Certificates of Deposit [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
3,495 |
|
Other Long-term Investments [Member] | Total [Member] | US Government Agencies Debt Securities [Member]
|
|
|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
Investments |
$ 46,061 |
|