INVESTMENTS: (Details) (USD $)	12 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011 Maximum	Dec. 31, 2012 Cash	Dec. 31, 2011 Cash	Dec. 31, 2011 Money market funds	Dec. 31, 2012 Certificates of deposits	Dec. 31, 2011 Certificates of deposits	Dec. 31, 2012 U.S. Government and agency securities	Dec. 31, 2011 U.S. Government and agency securities	Dec. 31, 2012 Commercial paper	Dec. 31, 2012 Corporate bonds	Dec. 31, 2011 Corporate bonds	Dec. 31, 2012 Foreign government bonds	Dec. 31, 2011 Foreign government bonds
Amortized Cost
Total investments in marketable securities	$ 419,795,000	$ 233,646,000		$ 110,148,000	$ 71,808,000	$ 105,246,000	$ 90,437,000	$ 50,170,000	$ 115,179,000	$ 250,000	$ 34,977,000	$ 61,543,000	$ 5,215,000	$ 7,511,000	$ 957,000
Less amounts classified as cash and cash equivalents	(117,054,000)	(181,258,000)
Short term investments, amortized cost	302,741,000	52,388,000
Estimated Fair Value
Short term investments, fair value	419,647,000	233,631,000		110,148,000	71,808,000	105,246,000	90,431,000	50,152,000	115,179,000	251,000	34,947,000	61,462,000	5,217,000	7,530,000	957,000
Less amounts classified as cash and cash equivalents	(117,054,000)	(181,258,000)
Short-term investments classified as available-for-sale securities	302,593,000	52,373,000
Net Unrealized Gains (Losses)
Gross Unrealized Gains (Losses)	(148,000)	(15,000)					(6,000)	(18,000)	(50,000)	1,000	(30,000)	(81,000)	2,000	19,000
Realized gains (losses) on sale of marketable securities	900,000		100,000
Amortized cost
Due in less than one year	58,758,000	42,670,000
Due in one to three years	243,983,000	9,718,000
Amortized cost	302,741,000	52,388,000
Estimated fair value
Due in less than one year	58,724,000	42,660,000
Due in one to three years	243,869,000	9,713,000
Estimated fair value	302,593,000	52,373,000
Investment in a privately-held company accounted for under the cost method	$ 4,400,000