INVESTMENTS: (Tables)

6 Months Ended

Jun. 30, 2016

Investments, Debt and Equity Securities [Abstract]

Schedule of cash, cash equivalents and short-term investments

The short-term investments are classified as available-for-sale securities. The cash, cash equivalents and short-term investments at June 30, 2016 and December 31, 2015 were as follows:

	June 30, 2016
	Amortized Cost			Unrealized Gains		Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash	$	58,516		$	—	$	—		$	58,516
Money market funds	4,985			—		—			4,985
Certificates of deposit	57,486			—		—			57,486
U.S. Government and agency securities	43,873			35		—			43,908
Commercial paper	28,363			—		—			28,363
Corporate bonds	74,608			73		(43		)	74,638
Municipal bonds	3,441			1		(1		)	3,441
Foreign government bonds	5,113			5		—			5,118
Total	276,385			114		(44		)	276,455
Less amounts classified as cash and cash equivalents	(63,501		)						(63,501		)
	$	212,884		$	114	$	(44	)	$	212,954

	December 31, 2015
	Amortized Cost			Unrealized Gains			Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash	$	65,524		$	—		$	—		$	65,524
Certificates of deposit	110,427			3			(7		)	110,423
U.S. Government and agency securities	131,755			5			(38		)	131,722
Commercial paper	57,214			4			(4		)	57,214
Corporate bonds	105,900			2			(420		)	105,482
Municipal bonds	26,283			—			(75		)	26,208
Foreign government bonds	13,988			—			(48		)	13,940
Total	511,091			14			(592		)	510,513
Less amounts classified as cash and cash equivalents	(263,196		)	(5		)	2			(263,199		)
	$	247,895		$	9		$	(590	)	$	247,314

Schedule of contractual maturities of short-term investments

The contractual maturities of short-term investments at June 30, 2016 and December 31, 2015 were as follows:

	June 30, 2016				December 31, 2015
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
	(in thousands)
Due in less than one year	$	133,643	$	133,686	$	148,041	$	147,914
Due in one to three years	79,241		79,268		99,854		99,400
	$	212,884	$	212,954	$	247,895	$	247,314