Investments (Tables)

12 Months Ended

Dec. 31, 2015

Investments

Schedule of marketable investments classified as held-to-maturity

        Marketable investments classified as held-to-maturity consist of the following (in thousands):

As of December 31, 2015	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Government-sponsored enterprises	$	53,254	$	3	$	(119	)	$	53,138
Corporate notes and bonds		106,722		37		(67	)		106,692
Total	$	159,976	$	40	$	(186	)	$	159,830
Reported under the following captions on the consolidated balance sheet:
Current marketable investments	$	121,974
Noncurrent marketable investments		38,002
	$	159,976

As of December 31, 2014	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Government-sponsored enterprises	$	127,212	$	118	$	(39	)	$	127,291
Corporate notes and bonds		293,288		260		(108	)		293,440
Total	$	420,500	$	378	$	(147	)	$	420,731
Reported under the following captions on the consolidated balance sheet:
Current marketable investments	$	297,842
Noncurrent marketable investments		122,658
	$	420,500

Summary of gross unrealized losses and the length of time marketable investments have been in a continuous unrealized loss position

        The following table summarizes gross unrealized losses and the length of time marketable investments have been in a continuous unrealized loss position (in thousands):

	As of December 31,
	2015					2014
	Fair Value		Gross Unrealized Loss			Fair Value		Gross Unrealized Loss
Government-sponsored enterprises:
Continuous unrealized loss position less than one year	$	48,138	$	(119	)	$	15,293	$	(39	)
Continuous unrealized loss position greater than one year		—		—			—		—
		48,138		(119	)		15,293		(39	)
Corporate notes and bonds:
Continuous unrealized loss position less than one year		63,840		(67	)		86,824		(97	)
Continuous unrealized loss position greater than one year		—		—			3,443		(11	)
		63,840		(67	)		90,267		(108	)
Total	$	111,978	$	(186	)	$	105,560	$	(147	)

Summary of the contractual maturities of held-to-maturity marketable investments

        The following table summarizes the contractual maturities of held-to-maturity marketable investments (in thousands):

	As of December 31, 2015
	Amortized Cost		Fair Value
Due in less than one year	$	121,974	$	121,932
Due in one to two years		38,002		37,898
Due in three to five years		—		—
Due after five years		—		—
Total	$	159,976	$	159,830