Available-for-Sale Securities and Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2018

Available-for-Sale Securities and Fair Value Measurements

Schedule of amortized cost and estimated fair values for available-for-sale securities

	September 30, 2018
			Gross		Gross
			Unrealized		Unrealized		Estimated
(In thousands)	Amortized Cost		Gains		Losses		Fair Value
U.S. corporate notes	$	3,876	$	—	$	(3)	$	3,873
U.S. commercial paper		7,988		—		—		7,988
Money market funds		38,685		—		—		38,685
Total	$	50,549	$	—	$	(3)	$	50,546

	December 31, 2017
			Gross		Gross
			Unrealized		Unrealized		Estimated
(In thousands)	Amortized Cost		Gains		Losses		Fair Value
U.S. government securities	$	9,943	$	—	$	(1)	$	9,942
U.S. government agencies		9,987		—		(2)		9,985
U.S. corporate notes		10,881		—		(15)		10,866
U.S. commercial papers		29,945		—		—		29,945
Money market funds		61,971		—		—		61,971
Total	$	122,727	$	—	$	(18)	$	122,709

Schedule of available-for-sale securities measured on a recurring basis

	Estimated Fair Value Measurements as of September 30, 2018 Using:
	Quoted Price in
	Active Markets		Significant Other		Significant
	for Identical		Observable		Unobservable
Types of Instruments	Assets		Inputs		Inputs
(In thousands)	Level 1		Level 2		Level 3		Total
Assets
U.S. corporate notes	$	—	$	3,873	$	—	$	3,873
U.S. commercial paper		—		7,988		—		7,988
Money market funds		38,685		—		—		38,685
Total assets measured at estimated fair value	$	38,685	$	11,861	$	—	$	50,546
Debt
Term B Loan	$	—	$	13,750	$	—	$	13,750
2023 Notes		—		247,310		—		247,310
2025 Notes		—		211,917		—		211,917
Total fair value of debt	$	—	$	472,977	$	—	$	472,977

	Estimated Fair Value Measurements as of December 31, 2017 Using:
	Quoted Price in
	Active Markets		Significant Other		Significant
	for Identical		Observable		Unobservable
Types of Instruments	Assets		Inputs		Inputs
(In thousands)	Level 1		Level 2		Level 3		Total
Assets
U.S. government securities	$	—	$	9,942	$	—	$	9,942
U.S. government agencies		—		9,985		—		9,985
U.S. corporate notes		—		10,866		—		10,866
U.S. commercial papers		—		29,945		—		29,945
Money market funds		61,971		—		—		61,971
Total assets measured at estimated fair value	$	61,971	$	60,738	$	—	$	122,709
Debt
Term B Loan	$	—	$	243,750	$	—	$	243,750
2023 Notes		—		241,259		—		241,259
2025 Notes		—		205,975		—		205,975
Total fair value of debt	$	—	$	690,984	$	—	$	690,984