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

3 Months Ended

Mar. 31, 2018

Available-for-Sale Securities and Fair Value Measurements

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

	March 31, 2018
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. government securities	$	9,978	$	—	$	(3	)	$	9,975
U.S. corporate notes	11,884		—		(19		)	11,865
U.S. commercial paper	12,476		—		—			12,476
Money market funds	17,118		—		—			17,118
Total	$	51,456	$	—	$	(22	)	$	51,434

	December 31, 2017
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated 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 March 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	$	—	$	9,975	$	—	$	9,975
U.S. corporate notes	—		11,865		—		11,865
U.S. commercial paper	—		12,476		—		12,476
Money market funds	17,118		—		—		17,118
Total assets measured at estimated fair value	$	17,118	$	34,316	$	—	$	51,434
Liabilities
Term B Loan	$	—	$	123,750	$	—	$	123,750
2023 Notes	—		259,058		—		259,058
2025 Notes	—		223,106		—		223,106
Total fair value of liabilities	$	—	$	605,914	$	—	$	605,914

	Estimated Fair Value Measurements as of December 31, 2017 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	$	—	$	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
Liabilities
Term B Loan	$	—	$	243,750	$	—	$	243,750
2023 Notes	—		241,259		—		241,259
2025 Notes	—		205,975		—		205,975
Total fair value of liabilities	$	—	$	690,984	$	—	$	690,984