FAIR VALUE MEASUREMENTS (Details) (USD $) | Jun. 30, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
FAIR VALUE MEASUREMENTS | ' | ' |
Transfers of assets between levels of the hierarchy | $0 | $0 |
Transfers of assets between levels of the hierarchy | 0 | 0 |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 208,506 | 161,194 |
Commercial Paper [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | ' | 9,992 |
US Treasury Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 20,000 | ' |
US Government-sponsored Enterprises Debt Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 1,001 | 4,000 |
Corporate Bond Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 140,862 | 101,660 |
Equity Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 2,754 | 3,549 |
Auction Rate Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 43,889 | 41,993 |
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Cash and cash equivalents | 225,226 | 483,868 |
Restricted cash | 2,071 | 3,560 |
Assets measured at fair value | 435,803 | 648,622 |
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Commercial Paper [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | ' | 9,992 |
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | US Treasury Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 20,000 | ' |
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | US Government-sponsored Enterprises Debt Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 1,001 | 4,000 |
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Corporate Bond Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 140,862 | 101,660 |
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Equity Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 2,754 | 3,549 |
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member] | Auction Rate Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 43,889 | 41,993 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Cash and cash equivalents | 225,226 | 483,868 |
Restricted cash | 2,071 | 3,560 |
Assets measured at fair value | 395,913 | 602,629 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | ' | 9,992 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 20,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Bond Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 140,862 | 101,660 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 2,754 | 3,549 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Auction Rate Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 5,000 | ' |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Assets measured at fair value | 1,001 | 4,000 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government-sponsored Enterprises Debt Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | 1,001 | 4,000 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Assets measured at fair value | 38,889 | 41,993 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Auction Rate Securities [Member] | ' | ' |
Assets and Liabilities Measured at Fair Value on a Recurring Basis | ' | ' |
Available-for-sale securities, fair value | $38,889 | $41,993 |