|
INVESTMENTS (Details) (USD $)
In Thousands, unless otherwise specified
|
3 Months Ended |
12 Months Ended |
|
Mar. 31, 2015
|
Dec. 31, 2014
|
| Held-to-maturity securities: |
|
|
| Estimated Fair Value |
$ 1,619 |
|
| Total investments |
|
|
| Amortized Cost |
595,983 |
577,864 |
| Gross Unrealized Gains |
527 |
127 |
| Gross Unrealized Losses, Less than One Year |
(106) |
(368) |
| Gross Unrealized Losses, Greater than One Year |
(4) |
(41) |
| Estimated Fair Value |
596,400 |
577,582 |
| Short-term investments |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
537,698 |
407,061 |
| Gross Unrealized Gains |
527 |
127 |
| Gross Unrealized Losses, Less than One Year |
(74) |
(86) |
| Estimated Fair Value |
538,151 |
407,102 |
| Short-term investments | U.S. government and agency debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
310,469 |
226,387 |
| Gross Unrealized Gains |
353 |
88 |
| Gross Unrealized Losses, Less than One Year |
(10) |
(15) |
| Estimated Fair Value |
310,812 |
226,460 |
| Short-term investments | Corporate debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
182,014 |
140,900 |
| Gross Unrealized Gains |
137 |
26 |
| Gross Unrealized Losses, Less than One Year |
(60) |
(66) |
| Estimated Fair Value |
182,091 |
140,860 |
| Short-term investments | International government agency debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
45,215 |
39,774 |
| Gross Unrealized Gains |
37 |
13 |
| Gross Unrealized Losses, Less than One Year |
(4) |
(5) |
| Estimated Fair Value |
45,248 |
39,782 |
| Long-term investments |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
56,666 |
169,184 |
| Gross Unrealized Losses, Less than One Year |
(32) |
(282) |
| Gross Unrealized Losses, Greater than One Year |
(4) |
(41) |
| Estimated Fair Value |
56,630 |
168,861 |
| Held-to-maturity securities: |
|
|
| Amortized Cost |
58,285 |
170,803 |
| Gross Unrealized Losses, Less than One Year |
(32) |
(282) |
| Gross Unrealized Losses, Greater than One Year |
(4) |
(41) |
| Estimated Fair Value |
58,249 |
170,480 |
| Long-term investments | Certificates of deposit |
|
|
| Held-to-maturity securities: |
|
|
| Amortized Cost |
1,619 |
1,619 |
| Estimated Fair Value |
1,619 |
1,619 |
| Long-term investments | U.S. government and agency debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
26,090 |
100,429 |
| Gross Unrealized Losses, Less than One Year |
(6) |
(196) |
| Gross Unrealized Losses, Greater than One Year |
(4) |
(40) |
| Estimated Fair Value |
26,080 |
100,193 |
| Long-term investments | Corporate debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
28,001 |
61,187 |
| Gross Unrealized Losses, Less than One Year |
(26) |
(84) |
| Estimated Fair Value |
27,975 |
61,103 |
| Long-term investments | International government agency debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
2,575 |
7,568 |
| Gross Unrealized Losses, Less than One Year |
|
(2) |
| Gross Unrealized Losses, Greater than One Year |
|
(1) |
| Estimated Fair Value |
$ 2,575 |
$ 7,565 |