Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2018

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)
September 30, 2018
Money market funds	$	112,829	$	—		$	—	$	112,829
Securities available-for-sale
Corporate debt		—		148,236			—		148,236
Trading securities
Corporate debt		—		83,381			—		83,381
Mutual funds held in rabbi trust		—		4,484			—		4,484
Foreign currency forward position		—		1,469			—		1,469
Total	$	112,829	$	237,570		$	—	$	350,399
December 31, 2017
Money market funds	$	88,562	$	—		$	—	$	88,562
Securities available-for-sale
Corporate debt		—		145,052			—		145,052
Trading securities
Corporate debt		—		91,302			—		91,302
Mutual funds held in rabbi trust		—		3,167			—		3,167
Foreign currency forward position		—		(702	)		—		(702	)
Total	$	88,562	$	238,819		$	—	$	327,381

Summary of Foreign Currency Forward Contracts

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

	As of
	September 30, 2018		December 31, 2017
	(In thousands)
Notional value	$	100,797	$	84,422
Fair value of notional		99,328		85,124
Fair value of the asset (liability)	$	1,469	$	(702	)

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 September 30, 2018
Securities available-for-sale
Corporate debt	$	148,981	$	14	$	(759	)	$	148,236
Trading securities
Corporate debt		83,891		10		(520	)		83,381
Mutual funds held in rabbi trust		4,347		—		137			4,484
Total trading securities		88,238		10		(383	)		87,865
Total investments	$	237,219	$	24	$	(1,142	)	$	236,101
December 31, 2017
Securities available-for-sale
Corporate debt	$	145,526	$	9	$	(483	)	$	145,052
Trading securities
Corporate debt		91,578		30		(306	)		91,302
Mutual funds held in rabbi trust		2,729		438		—			3,167
Total trading securities		94,307		468		(306	)		94,469
Total investments	$	239,833	$	477	$	(789	)	$	239,521

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
	September 30, 2018		December 31, 2017
	(In thousands)
Less than one year	$	140,544	$	130,738
Due in 1 - 5 years		95,557		108,783
Total	$	236,101	$	239,521

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 September 30, 2018 and December 31, 2017:

	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 September 30, 2018
Corporate debt	$	119,485	$	(716	)	$	60,425	$	(563	)	$	179,910	$	(1,279	)
As of December 31, 2017
Corporate debt	$	177,114	$	(536	)	$	26,476	$	(253	)	$	203,590	$	(789	)