Fair Value Measurements (Detail) - Fair Value Measurements at Reporting Date Using (USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
Investment Securities | $276,274 | $333,093 |
Estimate of Fair Value | ' | ' |
Investment Securities | ' | 333,093 |
Estimate of Fair Value | Cash equivalents | ' | ' |
Cash Equivalents | 581 | 43,678 |
Estimate of Fair Value | Short-term investments | ' | ' |
Investment Securities | 254,769 | 253,378 |
Estimate of Fair Value | Long-term investments | ' | ' |
Investment Securities | 276,274 | 36,037 |
Fair Value, Inputs, Level 1 | ' | ' |
Investment Securities | ' | 20,172 |
Fair Value, Inputs, Level 1 | Cash equivalents | ' | ' |
Cash Equivalents | 239 | 20,172 |
Fair Value, Inputs, Level 1 | Short-term investments | ' | ' |
Investment Securities | 0 | 0 |
Fair Value, Inputs, Level 1 | Long-term investments | ' | ' |
Investment Securities | 239 | 0 |
Fair Value, Inputs, Level 2 | ' | ' |
Investment Securities | ' | 312,921 |
Fair Value, Inputs, Level 2 | Cash equivalents | ' | ' |
Cash Equivalents | 342 | 23,506 |
Fair Value, Inputs, Level 2 | Short-term investments | ' | ' |
Investment Securities | 254,769 | 253,378 |
Fair Value, Inputs, Level 2 | Long-term investments | ' | ' |
Investment Securities | 276,035 | 36,037 |
Fair Value, Inputs, Level 3 | ' | ' |
Cash Equivalents | 0 | 0 |
Investment Securities | ' | 0 |
Fair Value, Inputs, Level 3 | Short-term investments | ' | ' |
Investment Securities | 0 | 0 |
Fair Value, Inputs, Level 3 | Long-term investments | ' | ' |
Investment Securities | 0 | 0 |
Money market funds | Estimate of Fair Value | Cash equivalents | ' | ' |
Cash Equivalents | 239 | 20,172 |
Money market funds | Fair Value, Inputs, Level 1 | Cash equivalents | ' | ' |
Cash Equivalents | 239 | 20,172 |
Money market funds | Fair Value, Inputs, Level 2 | ' | ' |
Cash Equivalents | 0 | 0 |
Money market funds | Fair Value, Inputs, Level 3 | ' | ' |
Cash Equivalents | 0 | 0 |
Commercial paper | Estimate of Fair Value | Short-term investments | ' | ' |
Investment Securities | 77,796 | 75,911 |
Commercial paper | Fair Value, Inputs, Level 1 | Short-term investments | ' | ' |
Investment Securities | 0 | 0 |
Commercial paper | Fair Value, Inputs, Level 2 | Short-term investments | ' | ' |
Investment Securities | 77,796 | 75,911 |
Commercial paper | Fair Value, Inputs, Level 3 | Short-term investments | ' | ' |
Investment Securities | 0 | 0 |
Municipal debt securities | Estimate of Fair Value | Cash equivalents | ' | ' |
Cash Equivalents | 342 | 23,506 |
Municipal debt securities | Estimate of Fair Value | Short-term investments | ' | ' |
Investment Securities | 117,915 | 122,325 |
Municipal debt securities | Estimate of Fair Value | Long-term investments | ' | ' |
Investment Securities | 20,924 | 36,037 |
Municipal debt securities | Fair Value, Inputs, Level 1 | ' | ' |
Cash Equivalents | 0 | 0 |
Municipal debt securities | Fair Value, Inputs, Level 1 | Short-term investments | ' | ' |
Investment Securities | 0 | 0 |
Municipal debt securities | Fair Value, Inputs, Level 1 | Long-term investments | ' | ' |
Investment Securities | 0 | 0 |
Municipal debt securities | Fair Value, Inputs, Level 2 | Cash equivalents | ' | ' |
Cash Equivalents | 342 | 23,506 |
Municipal debt securities | Fair Value, Inputs, Level 2 | Short-term investments | ' | ' |
Investment Securities | 117,915 | 122,325 |
Municipal debt securities | Fair Value, Inputs, Level 2 | Long-term investments | ' | ' |
Investment Securities | 20,924 | 36,037 |
Municipal debt securities | Fair Value, Inputs, Level 3 | ' | ' |
Cash Equivalents | 0 | 0 |
Municipal debt securities | Fair Value, Inputs, Level 3 | Short-term investments | ' | ' |
Investment Securities | 0 | 0 |
Municipal debt securities | Fair Value, Inputs, Level 3 | Long-term investments | ' | ' |
Investment Securities | 0 | 0 |
Corporate debt securities | Estimate of Fair Value | Short-term investments | ' | ' |
Investment Securities | 39,045 | 45,134 |
Corporate debt securities | Fair Value, Inputs, Level 1 | Short-term investments | ' | ' |
Investment Securities | 0 | 0 |
Corporate debt securities | Fair Value, Inputs, Level 2 | Short-term investments | ' | ' |
Investment Securities | 39,045 | 45,134 |
Corporate debt securities | Fair Value, Inputs, Level 3 | Short-term investments | ' | ' |
Investment Securities | 0 | 0 |
Government debt securities | Estimate of Fair Value | Short-term investments | ' | ' |
Investment Securities | 10,003 | 10,008 |
Government debt securities | Estimate of Fair Value | Long-term investments | ' | ' |
Investment Securities | 20,924 | ' |
Government debt securities | Fair Value, Inputs, Level 1 | Short-term investments | ' | ' |
Investment Securities | 0 | 0 |
Government debt securities | Fair Value, Inputs, Level 1 | Long-term investments | ' | ' |
Investment Securities | 0 | ' |
Government debt securities | Fair Value, Inputs, Level 2 | Short-term investments | ' | ' |
Investment Securities | 10,003 | 10,008 |
Government debt securities | Fair Value, Inputs, Level 2 | Long-term investments | ' | ' |
Investment Securities | 20,924 | ' |
Government debt securities | Fair Value, Inputs, Level 3 | Short-term investments | ' | ' |
Investment Securities | 0 | 0 |
Government debt securities | Fair Value, Inputs, Level 3 | Long-term investments | ' | ' |
Investment Securities | 0 | ' |
Certificates of deposit | Estimate of Fair Value | Short-term investments | ' | ' |
Investment Securities | 10,010 | ' |
Certificates of deposit | Fair Value, Inputs, Level 1 | Short-term investments | ' | ' |
Investment Securities | 0 | ' |
Certificates of deposit | Fair Value, Inputs, Level 2 | Short-term investments | ' | ' |
Investment Securities | 10,010 | ' |
Certificates of deposit | Fair Value, Inputs, Level 3 | Short-term investments | ' | ' |
Investment Securities | $0 | ' |