Cash, Cash Equivalents, and Marketable Securities

The following table summarizes the Company’s cash, cash equivalents, and marketable securities and the fair value categorization of the financial instruments measured at fair value on a recurring basis:



	March 31,		December 31,
	2018		2017
	(In thousands)
Cash	$	51,876	$	135,092
Time deposits	5,759		3,682
Money market funds (Level 1)	1,031,051		116,068
Debt securities issued by the U.S. Treasury (Level 1)	1,277,071		2,169,197
Total	$	2,365,757	$	2,424,039

Cash and cash equivalents	$	1,703,722	$	465,851
Restricted cash (included in Other long-term assets)	9,295		9,288
Total Cash, cash equivalents, and restricted cash	1,713,017		475,139
Marketable Securities	652,740		1,948,900
Total	$	2,365,757	$	2,424,039

The fair value of the debt securities held as of March 31, 2018 was $1.3 billion, including less than $0.1 million of gross and net unrealized gains. All of the debt securities held as of March 31, 2018 are scheduled to mature in less than one year. The higher Cash and cash equivalents balance and lower Marketable securities balance at March 31, 2018 reflects the short-term liquidity needed to settle the principal amount of the Subordinated Convertible Debentures in cash, upon redemption on May 1, 2018, as previously disclosed.

Fair Value Measurements

The fair value of the Company’s investments in money market funds approximates their face value. Such instruments are included in Cash and cash equivalents. The fair value of the debt securities consisting of U.S. Treasury bills is based on their quoted market prices. Debt securities purchased with original maturities in excess of three months are included in Marketable securities. The fair value of all of these financial instruments are classified as Level 1 in the fair value hierarchy.

The Company’s other financial instruments include cash, accounts receivable, restricted cash, and accounts payable. As of March 31, 2018, the carrying value of these financial instruments approximated their fair value. The fair value of the Company’s Subordinated Convertible Debentures was $4.3 billion as of March 31, 2018. The fair values of the senior notes due 2023 (the “2023 Senior Notes”), the senior notes due 2025 (the “2025 Senior Notes”), and the senior notes due 2027 (the “2027 Senior Notes”) were $751.9 million, $509.3 million, and $527.3 million, respectively, as of March 31, 2018. The fair values of these debt instruments are based on available market information from public data sources and are classified as Level 2.