INVESTMENTS (Details) - USD ($)
$ in Thousands |
Sep. 30, 2016 |
Dec. 31, 2015 |
| Held-to-maturity securities: |
|
|
| Estimated Fair Value |
$ 3,382
|
|
| Total investments |
|
|
| Amortized Cost |
422,167
|
$ 618,974
|
| Gross Unrealized Gains |
343
|
71
|
| Gross Unrealized Losses, Less than One Year |
(145)
|
(1,305)
|
| Estimated Fair Value |
422,365
|
617,740
|
| Short-term investments |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
346,918
|
353,957
|
| Gross Unrealized Gains |
343
|
71
|
| Gross Unrealized Losses, Less than One Year |
(43)
|
(359)
|
| Estimated Fair Value |
347,218
|
353,669
|
| Short-term investments | U.S. government and agency debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
193,228
|
141,789
|
| Gross Unrealized Gains |
219
|
51
|
| Gross Unrealized Losses, Less than One Year |
(1)
|
(104)
|
| Estimated Fair Value |
193,446
|
141,736
|
| Short-term investments | Corporate debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
142,692
|
175,098
|
| Gross Unrealized Gains |
108
|
20
|
| Gross Unrealized Losses, Less than One Year |
(41)
|
(179)
|
| Estimated Fair Value |
142,759
|
174,939
|
| Short-term investments | International government agency debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
10,998
|
37,070
|
| Gross Unrealized Gains |
16
|
|
| Gross Unrealized Losses, Less than One Year |
(1)
|
(76)
|
| Estimated Fair Value |
11,013
|
36,994
|
| Long-term investments |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
71,867
|
261,636
|
| Gross Unrealized Losses, Less than One Year |
(102)
|
(946)
|
| Estimated Fair Value |
71,765
|
260,690
|
| Held-to-maturity securities: |
|
|
| Amortized Cost |
3,382
|
3,381
|
| Estimated Fair Value |
3,382
|
3,381
|
| Long-term Investments |
|
|
| Total long-term investments |
75,249
|
265,017
|
| Gross Unrealized Losses, Less than one year |
(102)
|
(946)
|
| Total long-term investments |
75,147
|
264,071
|
| Long-term investments | Fixed Term Deposit Account |
|
|
| Held-to-maturity securities: |
|
|
| Amortized Cost |
1,667
|
1,666
|
| Estimated Fair Value |
1,667
|
1,666
|
| Long-term investments | Certificates of deposit |
|
|
| Held-to-maturity securities: |
|
|
| Amortized Cost |
1,715
|
1,715
|
| Estimated Fair Value |
1,715
|
1,715
|
| Long-term investments | U.S. government and agency debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
57,578
|
211,216
|
| Gross Unrealized Losses, Less than One Year |
(81)
|
(764)
|
| Estimated Fair Value |
57,497
|
210,452
|
| Long-term investments | Corporate debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
8,774
|
38,381
|
| Gross Unrealized Losses, Less than One Year |
(13)
|
(111)
|
| Estimated Fair Value |
8,761
|
38,270
|
| Long-term investments | International government agency debt securities |
|
|
| Available-for-sale securities: |
|
|
| Amortized Cost |
5,515
|
12,039
|
| Gross Unrealized Losses, Less than One Year |
(8)
|
(71)
|
| Estimated Fair Value |
$ 5,507
|
$ 11,968
|