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

3 Months Ended

Mar. 31, 2019

Available-for-Sale Securities and Fair Value Measurements

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

	March 31, 2019
			Gross		Gross
			Unrealized		Unrealized		Estimated
(In thousands)	Amortized Cost		Gains		Losses		Fair Value
U.S. government securities	$	68,691	$	9	$	—	$	68,700
U.S. government agencies		24,768		1		—		24,769
U.S. commercial paper		41,550		—		—		41,550
Money market funds		45,253		—		—		45,253
Total	$	180,262	$	10	$	—	$	180,272

	December 31, 2018
			Gross		Gross
			Unrealized		Unrealized		Estimated
(In thousands)	Amortized Cost		Gains		Losses		Fair Value
U.S. government securities	$	29,736	$	—	$	(3)	$	29,733
U.S. government agencies		4,971		—		—		4,971
U.S. corporate notes		2,875		—		—		2,875
U.S. commercial paper		22,037		—		—		22,037
Money market funds		49,358		—		—		49,358
Total	$	108,977	$	—	$	(3)	$	108,974

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

	Estimated Fair Value Measurements as of March 31, 2019 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	$	—	$	68,700	$	—	$	68,700
U.S. government agencies		—		24,769		—		24,769
U.S. commercial paper		—		41,550		—		41,550
Money market funds		45,253		—		—		45,253
Total assets measured at estimated fair value	$	45,253	$	135,019	$	—	$	180,272
Debt
Term B Loan	$	—	$	13,750	$	—	$	13,750
2023 Notes		—		245,353		—		245,353
2025 Notes		—		205,911		—		205,911
Total fair value of debt	$	—	$	465,014	$	—	$	465,014

	Estimated Fair Value Measurements as of December 31, 2018 Using:
Types of Instruments	Quoted Price in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
(In thousands)	Level 1		Level 2		Level 3		Total
Assets
U.S. government securities	$	—	$	29,733	$	—	$	29,733
U.S. government agencies		—		4,971		—		4,971
U.S. corporate notes		—		2,875		—		2,875
U.S. commercial paper		—		22,037		—		22,037
Money market funds		49,358		—		—		49,358
Total assets measured at estimated fair value	$	49,358	$	59,616	$	—	$	108,974
Debt
Term B Loan	$	—	$	13,750	$	—	$	13,750
2023 Notes		—		258,918		—		258,918
2025 Notes		—		230,692		—		230,692
Total fair value of debt	$	—	$	503,360	$	—	$	503,360