Investments (Tables)

12 Months Ended

Dec. 31, 2021

Investments Debt And Equity Securities [Abstract]

Gross Unrealized Gains and (Losses) Aggregated by Investment Category

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

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	$	22.0	$	—	$	—	$	22.0
Bankers' acceptance drafts		0.5		—		—		0.5
Commercial paper		41.8		—		—		41.8
U.S. treasury obligations		11.5		—		—		11.5
U.S. agency obligations		0.6		—		—		0.6
	$	76.4	$	—	$	—	$	76.4

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	$	5.3	$	0.9	$	—	$	6.2

As of December 31, 2020:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Short-term investments:
Available-for-sale investments:
Time deposits and certificates of deposit	$	0.7	$	—	$	—	$	0.7
Bankers' acceptance drafts		3.8		—		—		3.8
U.S. treasury obligations		223.2		—		—		223.2
	$	227.7	$	—	$	—	$	227.7

As of December 31, 2020:	Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Estimated Fair Value
Long-term investments:
Available-for-sale investments:
Group insurance contracts	$	5.6	$	0.9	$	—	$	6.5