The following tables show our cash, cash equivalents, restricted cash and short-term and long-term available-for-sale marketable debt securities, by major security type, that are measured at fair value on a recurring basis and were categorized using the fair value hierarchy, as well as their classification on our consolidated balance sheets, as of the periods presented (in millions):

	December 31, 2018
					Cash, Cash		Short-Term		Long-Term
	Amortized		Fair		Equivalents and		Marketable		Marketable
	Cost		Value (2)		Restricted Cash		Securities		Securities
Cash and restricted cash (1)	$	522	$	522	$	522	$	—	$	—
Level 1:
Money market funds		128		128		128		—		—
Level 2:
Commercial paper		20		20		5		15		—
Total	$	670	$	670	$	655	$	15	$	—

	December 31, 2017
					Cash, Cash		Short-Term		Long-Term
	Amortized		Fair		Equivalents and		Marketable		Marketable
	Cost		Value (2)		Restricted Cash		Securities		Securities
Cash and restricted cash (1)	$	663	$	663	$	663	$	—	$	—
Level 1:
Money market funds		1		1		1		—		—
Level 2:
U.S. agency securities		11		11		—		6		5
U.S. treasury securities		1		1		—		1		—
Certificates of deposit		2		2		—		2		—
Commercial paper		11		11		9		2		—
Corporate debt securities		46		46		—		24		22
Subtotal		71		71		9		35		27
Total	$	735	$	735	$	673	$	35	$	27

(1)	As of December 31, 2018 and 2017, our restricted cash, which primarily consists of escrowed security deposits, was not material and is included in other long-term assets on our consolidated balance sheets.

(2)	As of December 31, 2018 and 2017, any unrealized gains or losses related to our marketable securities were not material.

Our cash and cash equivalents consist of cash on hand in global financial institutions, money market funds and marketable securities, with maturities of 90 days or less at the date of purchase. The remaining maturities of our long-term marketable securities range from one to three years and our short-term marketable securities include maturities that were greater than 90 days at the date purchased and had 12 months or less remaining at December 31, 2018 and 2017, respectively.

We classify our cash, cash equivalents, restricted cash and marketable securities within Level 1 and Level 2 as we value these financial instruments using quoted market prices (Level 1) or alternative pricing sources (Level 2). The valuation technique we used to measure the fair value of money market funds was derived from quoted prices in active markets for identical assets or liabilities. Fair values for Level 2 marketable securities are considered “Level 2” valuations because they are obtained from independent pricing sources for identical or comparable instruments, rather than direct observations of quoted prices in active markets. Our procedures include controls to ensure that appropriate fair values are recorded, including comparing the fair values obtained from our independent pricing services against fair values obtained from another independent source.

There were no material realized gains or losses related to sales of our marketable securities for the years ended December 31, 2018, 2017 and 2016. We consider any unrealized loss positions in our available-for-sale marketable debt securities to be temporary in nature and do not consider any of these investments other-than-temporarily impaired as of December 31, 2018 and December 31, 2017.

We typically use derivatives, or forward contracts, to reduce the effects of foreign currency exchange rate fluctuations on our cash flows primarily for the Euro versus the U.S. Dollar. For the periods ended December 31, 2018, 2017 and 2016, our forward contracts have not been designated as hedges and have typically had maturities of less than 90 days.

Our outstanding or unsettled forward contracts are carried at fair value on our consolidated balance sheets at December 31, 2018. Any gain or loss resulting from the change in fair value of our forward contracts for the years ended December 31, 2018, 2017 and 2016, has been recognized in our consolidated statement of operations in “Interest income and other, net.” We recorded a net loss of $3 million and $1 million for the years ended December 31, 2018 and 2017, respectively, and a net gain of $2 million for the year ended December 31, 2016, related to our forward contracts.

The following table shows the notional principal amounts of our outstanding derivative instruments for the periods presented:

Other financial instruments not measured at fair value on a recurring basis include accounts receivable and contract assets, accounts payable, deferred merchant payables, short-term debt, accrued expenses and other current liabilities and long-term debt. The carrying amount of these financial instruments, with the exception of long-term debt, approximate their fair value because of the short maturity of these instruments as reported on our consolidated balance sheets as of December 31, 2018 and December 31, 2017, respectively. The carrying value of any long-term debt from our 2015 Credit Facility bears interest at a variable rate and therefore is also considered to approximate fair value.

In addition, we hold investments in equity securities of privately-held companies that do not have a readily determinable fair value. As of both December 31, 2018 and 2017, respectively, the total carrying value of our equity investments in these privately-held companies were $12 million and are included in other long-term assets on our consolidated balance sheets. Our policy is to measure these investments at cost less impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer such observable price changes may include instances where the investee issues equity securities to new investors, thus creating a new indicator of fair value, as an example. On a quarterly basis, we perform a qualitative assessment considering impairment indicators to evaluate whether these investments are impaired and also monitor for any observable price changes. During the year ended December 31, 2018, we did not have any impairment loss on these equity investments. The Company recognized a loss of $2 million related to one of our equity investments during the year ended December 31, 2017 in “Interest income and other, net” on our consolidated statements of operations.

The Company did not have any material assets or liabilities measured at fair value on a recurring basis using Level 3 unobservable inputs at both December 31, 2018 and December 31, 2017.