SHARE-BASED COMPENSATION - Schedule of Share-based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	$ 8.4	$ 3.8	$ 14.8	$ 8.4
Loss and loss adjustment expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	0.8	0.4	1.4	0.8
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	0.3	0.2	0.5	0.3
Other insurance expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	0.2	0.1	0.5	0.3
Technology and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	1.5	0.7	2.8	1.5
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	$ 5.6	$ 2.4	$ 9.6	$ 5.5

Root, Inc. 10-Q