FAIR VALUE MEASUREMENTS: (Details) (Fair Value, Measurements, Recurring Basis, USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Level 1
Financial assets and liabilities measured at fair value
Financial assets		$ 105,246
Level 1 | Money market funds
Financial assets and liabilities measured at fair value
Financial assets		105,246
Level 2
Financial assets and liabilities measured at fair value
Financial assets	312,441	56,577
Financial liabilities		1,149
Level 2 | Certificates of deposits
Financial assets and liabilities measured at fair value
Financial assets	90,431	50,152
Level 2 | U.S. Government and agency securities
Financial assets and liabilities measured at fair value
Financial assets	115,129	251
Level 2 | Commercial paper
Financial assets and liabilities measured at fair value
Financial assets	34,947
Level 2 | Corporate bonds
Financial assets and liabilities measured at fair value
Financial assets	61,462	5,217
Level 2 | Foreign government bonds
Financial assets and liabilities measured at fair value
Financial assets	7,530	957
Level 2 | Forward contracts
Financial assets and liabilities measured at fair value
Financial assets	2,942
Financial liabilities		1,149
Total
Financial assets and liabilities measured at fair value
Financial assets		161,823
Financial liabilities		1,149
Total | Money market funds
Financial assets and liabilities measured at fair value
Financial assets		105,246
Total | Certificates of deposits
Financial assets and liabilities measured at fair value
Financial assets	90,431	50,152
Total | U.S. Government and agency securities
Financial assets and liabilities measured at fair value
Financial assets	115,129	251
Total | Commercial paper
Financial assets and liabilities measured at fair value
Financial assets	34,947
Total | Corporate bonds
Financial assets and liabilities measured at fair value
Financial assets	61,462	5,217
Total | Foreign government bonds
Financial assets and liabilities measured at fair value
Financial assets	7,530	957
Total | Forward contracts
Financial assets and liabilities measured at fair value
Financial assets	2,942
Financial liabilities		$ 1,149