Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2019

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
	(In thousands)
As of December 31, 2019
Money market funds	$	99,755	$	—		$	—	$	99,755
Securities available-for-sale
Corporate debt		—		137,835			—		137,835
Trading securities
Corporate debt		—		31,120			—		31,120
U.S. Treasuries		—		55,305			—		55,305
Mutual funds held in rabbi trust		—		6,217			—		6,217
Foreign currency forward position		—		(2,772	)		—		(2,772	)
Total	$	99,755	$	227,705		$	—	$	327,460
As of December 31, 2018
Money market funds	$	112,529	$	—		$	—	$	112,529
Securities available-for-sale
Corporate debt		—		146,966			—		146,966
Trading securities
Corporate debt		—		71,861			—		71,861
U.S. Treasuries		—		17,178			—		17,178
Mutual funds held in rabbi trust		—		4,100			—		4,100
Foreign currency forward position		—		(1,021	)		—		(1,021	)
Total	$	112,529	$	239,084		$	—	$	351,613

Summary of Foreign Currency Forward Contracts

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

	As of December 31,
	2019			2018
	(In thousands)
Notional value	$	155,885		$	106,306
Fair value of notional		158,657			107,327
Fair value of the (liability)	$	(2,772	)	$	(1,021	)

Summary of Company's Investments

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

	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value
	(In thousands)
As of December 31, 2019
Securities available-for-sale
Corporate debt	$	137,119	$	721	$	(5	)	$	137,835
Trading securities
Corporate debt		31,120		14		(14	)		31,120
U.S. Treasuries		54,738		567		—			55,305
Mutual funds held in rabbi trust		5,173		1,044		—			6,217
Total trading securities		91,031		1,625		(14	)		92,642
Total investments	$	228,150	$	2,346	$	(19	)	$	230,477
As of December 31, 2018
Securities available-for-sale
Corporate debt	$	147,556	$	27	$	(617	)	$	146,966
Trading securities
Corporate debt		72,274		8		(421	)		71,861
U.S. Treasuries		16,953		225		—			17,178
Mutual funds held in rabbi trust		4,347		—		(247	)		4,100
Total trading securities		93,574		233		(668	)		93,139
Total investments	$	241,130	$	260	$	(1,285	)	$	240,105

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,
	2019		2018
	(In thousands)
Less than one year	$	120,850	$	134,255
Due in 1 - 5 years		109,627		105,850
Total	$	230,477	$	240,105

Fair Values and Unrealized Losses on Corporate Debt Investments

The following table provides fair values and unrealized losses on corporate debt investments and by the aging of the securities' continuous unrealized loss position as of December 31, 2019 and 2018 respectively:  

	Less than Twelve Months					Twelve Months or More					Total
	Estimated fair value		Gross unrealized losses			Estimated fair value		Gross unrealized losses			Estimated fair value		Gross unrealized losses
	(In thousands)
As of December 31, 2019
Corporate debt	$	27,999	$	(18	)	$	4,406	$	(1	)	$	32,405	$	(19	)
As of December 31, 2018
Corporate debt	$	80,282	$	(256	)	$	87,028	$	(782	)	$	167,310	$	(1,038	)