Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Valuation of Company's Assets and Liabilities Measured at Fair Value

The following table summarizes the valuation of the Company’s assets and liabilities measured at fair value as categorized based on the hierarchy described in Note 2.

	Level 1		Level 2			Level 3		Total
As of December 31, 2016	(In thousands)
Money market funds	$	58,573	$	—		$	—	$	58,573
Securities available-for-sale
Corporate debt		—		118,870			—		118,870
Trading securities
Corporate debt				74,207					74,207
Mutual funds held in rabbi trust		—		1,327			—		1,327
Foreign currency forward position		—		(266	)		—		(266	)
Total	$	58,573	$	194,138		$	—	$	252,711
As of December 31, 2015
Money market funds	$	61,913	$	—		$	—	$	61,913
Securities available-for-sale
Corporate debt		—		82,671			—		82,671
Municipal securities		—		2,035			—		2,035
Foreign currency forward position		—		354			—		354
Total	$	61,913	$	85,060		$	—	$	146,973

Summary of Foreign Currency Forward Contracts

A summary of the foreign currency forward position is as follows:

	As of December 31,
		2016			2015
	(In thousands)
Notional value	$	66,972		$	45,716
Fair value of notional		67,238			45,362
Fair value of the (liability) asset	$	(266	)	$	354

Summary of Company's Investments

The following is a summary of the Company’s investments:

			Gross		Gross			Estimated
	Amortized		unrealized		unrealized			fair
	cost		gains		losses			value
	(In thousands)
As of December 31, 2016
Securities available-for-sale
Corporate debt	$	119,073	$	13	$	(216	)	$	118,870
Trading securities
Corporate debt	$	74,394	$	47	$	(234	)	$	74,207
Mutual funds held in rabbi trust		1,212		115		—			1,327
Total trading securities	$	75,606	$	162	$	(234	)	$	75,534
Total investments	$	194,679	$	175	$	(450	)	$	194,404
As of December 31, 2015
Securities available-for-sale
Corporate debt	$	82,937	$	4	$	(270	)	$	82,671
Municipal securities		2,035		—		—			2,035
Total securities available-for-sale	$	84,972	$	4	$	(270	)	$	84,706

Summary of Fair Value of Investments Based upon Contractual Maturities

The following table summarizes the fair value of the investments based upon the contractual maturities:

	As of December 31,
		2016		2015
	(In thousands)
Less than one year	$	117,904	$	37,694
Due in 1 - 5 years		76,500		47,012
Total	$	194,404	$	84,706

Fair Values and Unrealized Losses on Investments

The following table provides fair values and unrealized losses on investments and by the aging of the securities' continuous unrealized loss position as of December 31, 2016 and 2015 respectively:  

	Less than Twelve Months					Twelve Months or More					Total
	Estimated		Gross			Estimated		Gross			Estimated		Gross
	fair		unrealized			fair		unrealized			fair		unrealized
	value		losses			value		losses			value		losses
	(In thousands)
As of December 31, 2016
Corporate debt	$	136,667	$	(449	)	$	2,000	$	(1	)	$	138,667	$	(450	)
As of December 31, 2015
Corporate debt	$	70,651	$	(270	)	$	—	$	—		$	70,651	$	(270	)