CASH, CASH EQUIVALENTS, AND INVESTMENTS

The following tables summarize the Company’s cash and available-for-sale securities’ amortized cost, gross unrealized gains, gross unrealized losses, and fair value by significant investment category recorded as cash and cash equivalents, short-term, or long-term investments as of December 31, 2017 and March 31, 2017 (in thousands):



December 31, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Cash & Cash Equivalents		Short-term investments (due in 1 year or less)		Long-term investments (due in 1 to 3 years)
Cash	$	272,063	$	—	$	—		$	272,063	$	272,063	$	—	$	—
Level 1:
Mutual Funds	14,298		399		(70		)	14,627		—		14,627		—
US Treasury Notes	71,684		—		(210		)	71,474		4,998		42,348		24,128
Money Market Funds	239		—		—			239		239		—		—
Subtotal	86,221		399		(280		)	86,340		5,237		56,975		24,128
Level 2:
Government Agency Securities	56,667		—		(276		)	56,391		—		31,300		25,091
Commercial Paper	32,944		—		—			32,944		2,993		29,951		—
Corporate Bonds	142,148		45		(375		)	141,818		—		77,175		64,643
Certificates of Deposits ("CDs")	28,383		—		(3		)	28,380		—		23,372		5,008
Subtotal	260,142		45		(654		)	259,533		2,993		161,798		94,742

Total cash, cash equivalents and investments measured at fair value	$	618,426	$	444	$	(934	)	$	617,936	$	280,293	$	218,773	$	118,870



March 31, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Cash & Cash Equivalents		Short-term investments (due in 1 year or less)		Long-term investments (due in 1 to 3 years)
Cash	$	295,877	$	—	$	—		$	295,877	$	295,877	$	—	$	—
Level 1:
Mutual Funds	12,079		352		(32		)	12,399		—		12,399		—
US Treasury Notes	35,960		—		(68		)	35,892		—		17,560		18,332
Money Market Funds	—		—		—			—		—		—		—
Subtotal	48,039		352		(100		)	48,291		—		29,959		18,332
Level 2:
Government Agency Securities	54,415		20		(164		)	54,271		—		15,309		38,962
Commercial Paper	47,152		—		—			47,152		6,093		41,059		—
Corporate Bonds	141,508		64		(224		)	141,348		—		73,676		67,672
Certificates of Deposits ("CDs")	20,383		3		—			20,386		—		18,176		2,210
Subtotal	263,458		87		(388		)	263,157		6,093		148,220		108,844

Total cash, cash equivalents and investments measured at fair value	$	607,374	$	439	$	(488	)	$	607,325	$	301,970	$	178,179	$	127,176

As of December 31, 2017 and March 31, 2017, with the exception of assets related to the Company's deferred compensation plan, all of the Company's investments are classified as available-for-sale securities. The carrying value of available-for-sale securities included in cash equivalents approximates fair value because of the short maturity of those instruments. For more information regarding the Company's deferred compensation plan, refer to Note 4, Deferred Compensation.

The Company did not incur any material realized or unrealized gains or losses in the three and nine months ended December 31, 2016 and 2017.

There were no transfers between fair value measurement levels during the three and nine months ended December 31, 2016 and 2017.

All financial assets and liabilities are recognized or disclosed at fair value in the financial statements or the accompanying notes thereto. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement:

Level 1

The Company's Level 1 financial assets consist of Mutual Funds and US Treasury Notes. The fair value of Level 1 financial instruments is measured based on the quoted market price of identical securities.

Level 2

The Company's Level 2 financial assets and liabilities consist of Government Agency Securities, Commercial Paper, Corporate Bonds, and Certificates of Deposits ("CDs"), derivative foreign currency contracts, and long-term debt. The fair value of Level 2 investment securities is determined based on other observable inputs, including multiple non-binding quotes from independent pricing services. Non-binding quotes are based on proprietary valuation models that are prepared by the independent pricing services and use algorithms based on inputs such as observable market data, quoted market prices for similar securities, issuer spreads, and internal assumptions of the broker. The Company corroborates the reasonableness of non-binding quotes received from the independent pricing services using a variety of techniques depending on the underlying instrument, including: (i) comparing them to actual experience gained from the purchases and maturities of investment securities, (ii) comparing them to internally developed cash flow models based on observable inputs, and (iii) monitoring changes in ratings of similar securities and the related impact on fair value. The fair value of Level 2 derivative foreign currency contracts is determined using pricing models that use observable market inputs. For more information regarding the Company's derivative assets and liabilities, refer to Note 12, Foreign Currency Derivatives. The fair value of Level 2 long-term debt is determined based on inputs that were observable in the market, including the trading price of the notes when available. For more information regarding the Company's 5.50% Senior Notes, refer to Note 7, Debt.

Level 3

The Company's unsecured revolving credit facility falls under the Level 3 hierarchy. The fair value of the Company’s line of credit approximates its carrying value because the interest rate is variable and approximates rates currently available to the Company.