Marketable Securities and Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2017

Notes To Financial Statements [Abstract]

Short-Term And Long-Term Marketable Securities

As of March 31, 2017 and December 31, 2016, the estimated fair value of our short-term and long-term marketable securities, classified as available for sale, are as follows (in thousands):

Short-term

March 31, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Commercial paper	$	42,160	$	—	$	—		$	42,160
Corporate bonds	152,169		30		(107		)	152,092
Municipal securities	3,853		—		(1		)	3,852
U.S. government agency bonds	21,879		—		(16		)	21,863
U.S. government treasury bonds	54,767		—		(28		)	54,739
Certificates of deposit	9,787		—		—			9,787
Asset-backed securities	66		—		—			66
Total marketable securities, short-term	$	284,681	$	30	$	(152	)	$	284,559

Long-term

March 31, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. government agency bonds	$	11,295	$	19	$	(12	)	$	11,302
Corporate bonds	79,267		48		(65		)	79,250
U.S. government treasury bonds	8,034		3		(15		)	8,022
Total marketable securities, long-term	$	98,596	$	70	$	(92	)	$	98,574

Short-term

December 31, 2016	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Commercial paper	$	42,397	$	—	$	(6	)	$	42,391
Corporate bonds	122,788		22		(121		)	122,689
Municipal securities	5,852		—		(5		)	5,847
U.S. government agency bonds	28,903		9		(4		)	28,908
U.S. government treasury bonds	45,146		7		(7		)	45,146
Certificates of deposit	6,000		—		—			6,000
Total marketable securities, short-term	$	251,086	$	38	$	(143	)	$	250,981

Long-term

December 31, 2016	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. government agency bonds	$	6,805	$	—	$	(16	)	$	6,789
Corporate bonds	40,889		8		(85		)	40,812
U.S. government treasury bonds	12,016		5		(16		)	12,005
Asset-backed securities	177		—		—			177
Total marketable securities, long-term	$	59,887	$	13	$	(117	)	$	59,783

Investments Classified by Contractual Maturity Date [Table Text Block]

As the carrying value approximates the fair value for our short-term and long-term marketable securities shown in the tables above, the following table summarizes the fair value of our short-term and long-term marketable securities classified by maturity as of March 31, 2017 and December 31, 2016 (in thousands):

	March 31, 2017		December 31, 2016
One year or less	$	284,559	$	250,981
Due in greater than one year	98,574		59,783
Total available for sale short-term and long-term marketable securities	$	383,133	$	310,764

Financial Assets Measured At Fair Value On Recurring Basis

The following tables summarize our financial assets measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016 (in thousands):

Description	Balance as of March 31, 2017		Quoted Prices in Active  Markets for Identical Assets (Level 1)		Significant Other Observable  Inputs (Level 2)		Significant Other Observable  Inputs (Level 3)
Cash equivalents:
Money market funds	$	141,256	$	141,256	$	—	$	—
Commercial paper	20,026		—		20,026		—
U.S. government treasury bonds	5,521		5,521		—		—
Municipal securities	2,001		—		2,001		—
Short-term investments:
Commercial paper	42,160		—		42,160		—
Corporate bonds	152,092		—		152,092		—
Municipal securities	3,852		—		3,852		—
U.S. government agency bonds	21,863		—		21,863		—
U.S. government treasury bonds	54,739		54,739		—		—
Certificates of deposit	9,787		—		9,787		—
Asset-backed securities	66		—		66		—
Long-term investments:
U.S. government agency bonds	11,302		—		11,302		—
Corporate bonds	79,250		—		79,250		—
U.S. government treasury bonds	8,022		8,022		—		—
Prepaid expenses and other current assets:
Israeli funds	3,191		—		3,191		—
Other assets:
Long-term notes receivable	2,084		—		—		2,084
	$	557,212	$	209,538	$	345,590	$	2,084

Description	Balance as of December 31, 2016		Quoted Prices in Active  Markets for Identical Assets (Level 1)		Significant Other Observable  Inputs (Level 2)		Significant Other Observable  Inputs (Level 3)
Cash equivalents:
Money market funds	$	87,179	$	87,179	$	—	$	—
Commercial paper	2,499		—		2,499		—
Corporate bonds	750		—		750		—
Short-term investments:
Commercial paper	42,391		—		42,391		—
Corporate bonds	122,689		—		122,689		—
Municipal securities	5,847		—		5,847		—
U.S. government agency bonds	28,908		—		28,908		—
U.S. government treasury bonds	45,146		45,146		—		—
Certificates of deposit	6,000		—		6,000		—
Long-term investments:
U.S. government agency bonds	6,789		—		6,789		—
Corporate bonds	40,812		—		40,812		—
U.S. government treasury bonds	12,005		12,005		—		—
Asset-backed securities	177		—		177		—
Prepaid expenses and other current assets:
Israeli funds	2,956		—		2,956		—
Other assets:
Long-term notes receivable	2,047		—		—		2,047
	$	406,195	$	144,330	$	259,818	$	2,047