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


As of June 30, 2022:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Short-term investments:
Time deposits and certificates of deposit	$	1	$	—	$	—	$	1
Banker's acceptance drafts		1		—		—		1
	$	2	$	—	$	—	$	2


As of June 30, 2022:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Long-term 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:
Group insurance contracts	$	5	$	1	$	—	$	6

Management has the ability to liquidate certain of the Company's investments in order to meet the Company's liquidity needs in the next 12 months. Accordingly, certain 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." The cost of marketable securities sold is determined by the specific identification method. Realized gains or losses are reflected in income and were not material for the six months ended June 30, 2022 and 2021.