Financial Instruments

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:



	As of December 31,
	2017		2016
	(In thousands)
Cash	$	135,092	$	39,183
Time deposits	3,682		4,632
Money market funds (Level 1)	116,068		134,790
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies (Level 1)	2,169,172		1,626,764
Equity securities of public companies (Level 1)	25		2,174
Total	$	2,424,039	$	1,807,543

Included in Cash and cash equivalents	$	465,851	$	231,945
Included in Marketable securities	1,948,900		1,565,962
Included in Other assets (Restricted cash)	9,288		9,636
Total	$	2,424,039	$	1,807,543

The fair value of the debt securities held as of December 31, 2017 was $2.2 billion, including less than $1.0 million of gross and net unrealized losses. All of the debt securities held as of December 31, 2017 have contractual maturities of less than one year.

Fair Value Measurements

The fair value of the Company’s investments in money market funds approximates their face value. Such instruments are classified as Level 1 and 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 and are classified as Level 1. Debt securities purchased with original maturities in excess of three months are included in Marketable securities. Debt securities purchased with original maturities less than three months are included in Cash and cash equivalents.

The fair value of the equity securities of public companies is based on quoted market prices and are classified as Level 1. Investments in equity securities of public companies are included in marketable securities.

As of December 31, 2017, the Company’s other financial instruments include cash, accounts receivable, restricted cash, and accounts payable whose carrying values approximated their fair values. The fair value of the Company’s Subordinated Convertible Debentures was $4.2 billion as of December 31, 2017. The fair values of the Company’s 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 $772.9 million, $544.4 million, and $563.7 million, respectively, as of December 31, 2017. The fair values of these debt instruments are based on available market information from public data sources and are classified as Level 2.