INVESTMENTS (Tables)

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Schedule of Carrying Amounts of Investment Securities and Fair Values

The amortized cost, gross unrealized gains and losses and estimated fair values of debt securities available-for-sale, equity securities, and other investments measured at net asset value are as follows:

	As of December 31, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In millions)
Short-term investments	$	6.3	$	—	$	(0.1)	$	6.2
U.S Treasury	13.6		0.1		(0.1)		13.5
Municipal	30.1		0.2		(0.2)		30.1
Corporate	131.5		1.6		(0.9)		132.2
Mortgage and other asset-backed securities	150.1		1.6		(0.9)		150.9
Total debt securities	331.6		3.5		(2.2)		332.9
Total investments	$	331.6	$	3.5	$	(2.2)	$	332.9

	As of December 31, 2022
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In millions)
Short-term investments	$	5.4	$	—	$	—	$	5.4
U.S Treasury	11.8		—		(0.2)		11.6
Municipal	22.8		—		(0.4)		22.4
Corporate	81.8		0.2		(2.3)		79.7
Mortgage and other asset-backed securities	73.8		0.3		(1.4)		72.7
Total debt securities	195.5		0.5		(4.4)		191.7
Common stock	48.7		—		—		48.7
Total investments	$	244.2	$	0.5	$	(4.4)	$	240.4

Schedule of Amortized Cost and Fair Value of TCA's Investment

A summary of amortized costs and fair value of investments by time to maturity, is as follows:

	As of December 31, 2023
	Amortized Costs		Fair Value
	(In millions)
Due in 1 year or less	$	6.3	$	6.2
Due in 1-5 years	116.9		116.9
Due in 5-10 years	52.9		53.4
Due after 10 years	5.4		5.5
Total by maturity	181.5		182.0
Mortgage and other asset-backed securities	150.1		150.9
Total investment securities	$	331.6	$	332.9

Schedule of Unrealized Loss on Investments

The following tables summarize the amount of unrealized losses, defined as the amount by which the amortized cost exceeds fair value, and the related fair value of investments with unrealized losses. The investments were segregated into two categories: those that have been in a continuous unrealized loss position for less than 12 months and those that have been in a continuous unrealized loss position of 12 or more months. The reference point for determining how long an investment was in an unrealized loss position was December 31, 2023.

	As of December 31, 2023
	Less than 12 Months				Greater than 12 Months				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(In millions)
Short-term investments	$	—	$	—	$	6.0	$	(0.1)	$	6.0	$	(0.1)
U.S Treasury	3.4		(0.1)		5.0		(0.1)		8.5		(0.1)
Municipal	6.4		(0.1)		10.4		(0.1)		16.8		(0.2)
Corporate	11.4		(0.1)		48.0		(0.8)		59.4		(0.9)
Mortgage and other asset-backed securities	29.8		(0.4)		33.1		(0.5)		62.9		(0.9)
Total debt securities	$	51.1	$	(0.7)	$	102.5	$	(1.6)	$	153.6	$	(2.2)

	As of December 31, 2022
	Less than 12 Months				Greater than 12 Months				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(In millions)
U.S Treasury	$	9.2	$	(0.2)	$	—	$	—	$	9.2	$	(0.2)
Municipal	19.0		(0.4)		—		—		19.0		(0.4)
Corporate	66.2		(0.1)		5.2		(0.3)		71.4		(0.4)
Mortgage and other asset-backed securities	51.4		(1.3)		1.5		(0.2)		52.9		(1.5)
Total debt securities	$	145.7	$	(2.0)	$	6.8	$	(0.5)	$	152.6	$	(2.5)