The following table shows the gross unrealized gains and (losses) aggregated by investment category for available-for-sale investments:


As of December 31, 2022	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Short-term investments:
Available-for-sale investments:
Time deposits and certificates of deposit	$	1	$	—	$	—	$	1
	$	1	$	—	$	—	$	1


As of December 31, 2022:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Long-term investments:
Available-for-sale investments:
Group insurance contracts	$	5	$	1	$	—	$	6


As of December 31, 2021:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Short-term investments:
Available-for-sale investments:
Time deposits and certificates of deposit	$	22	$	—	$	—	$	22
Commercial paper		42		—		—		42
U.S. treasury obligations		11		—		—		11
U.S. agency obligations		1		—		—		1
	$	76	$	—	$	—	$	76


As of December 31, 2021	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Long-term investments:
Available-for-sale investments:
Group insurance contracts	$	5	$	1	$	—	$	6

The tables above, which show the gross unrealized gains and (losses) aggregated by investment category for available-for-sale investments as of December 31, 2022 and 2021, reflect the inclusion within short-term investments of investments with contractual maturities greater than one year from the date of purchase. Management has the ability, if necessary, to liquidate any of its investments in order to meet the Company’s liquidity needs in the next 12 months. Accordingly, those investments with contractual maturities greater than one year from the date of purchase are classified as short-term on the accompanying balance sheets.

Interest income is accrued as earned. Dividend income is recognized as income on the date the security trades “ex-dividend.” Realized gains or losses are reflected in income and were not material in 2022, 2021 and 2020.