Financial Instruments and Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2020

Financial Instruments and Fair Value Measurements

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

Available-for-sale securities are summarized below:

	March 31, 2020
			Gross		Gross
			Unrealized		Unrealized		Estimated
(In thousands)	Amortized Cost		Gains		Losses		Fair Value
U.S. government securities	$	13,958	$	41	$	—	$	13,999
U.S. commercial paper		48,964		—		—		48,964
Money market funds		285,309		—		—		285,309
Total	$	348,231	$	41	$	—	$	348,272

	December 31, 2019
			Gross		Gross
			Unrealized		Unrealized		Estimated
(In thousands)	Amortized Cost		Gains		Losses		Fair Value
U.S. government securities	$	53,799	$	35	$	—	$	53,834
U.S. commercial paper		18,915		—		—		18,915
Money market funds		233,992		—		—		233,992
Total	$	306,706	$	35	$	—	$	306,741

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

The estimated fair values were as follows:

	Estimated Fair Value Measurements as of March 31, 2020 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	$	—	$	13,999	$	—	$	13,999
U.S. commercial paper		—		48,964		—		48,964
Money market funds		285,309		—		—		285,309
Equity investment - Armata Common Stock		27,003		—		—		27,003
Equity investment - Armata Warrants		—		19,912		—		19,912
Total assets measured at estimated fair value	$	312,312	$	82,875	$	—	$	395,187
Debt
2023 Notes	$	—	$	216,886	$	—	$	216,886
2025 Notes		—		191,538		—		191,538
Total fair value of debt	$	—	$	408,424	$	—	$	408,424

	Estimated Fair Value Measurements as of December 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	$	—	$	53,834	$	—	$	53,834
U.S. commercial paper		—		18,915		—		18,915
Money market funds		233,992		—		—		233,992
Total assets measured at estimated fair value	$	233,992	$	72,749	$	—	$	306,741
Debt
2023 Notes	$	—	$	243,394	$	—	$	243,394
2025 Notes		—		208,976		—		208,976
Total fair value of debt	$	—	$	452,370	$	—	$	452,370