DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($) state dealership franchise vehicleBrand collisionCenter shares	Sep. 30, 2023 shares	Sep. 30, 2024 USD ($) state segment dealership franchise vehicleBrand collisionCenter shares	Sep. 30, 2023 USD ($) shares	May 15, 2024 USD ($)	May 14, 2024 USD ($)
Business Organization [Line Items]
Number of franchises (in franchises) | franchise	202		202
Number of dealership locations (in dealership locations) | dealership	153		153
Number of vehicle brands (in vehicle brands) | vehicleBrand	31		31
Number of collision repair centers (in collision repair centers) | collisionCenter	37		37
Number of states (in states) | state	14		14
Number of reportable segments | segment			2
Shares repurchased (in shares) | shares	393,951	0	826,340	1,070,126
Treasury stock, retired (in shares) | shares	393,951	0	826,340	1,124,330
Cash paid to acquire treasury stock | $			$ 182.1	$ 210.7
Stock repurchase program, increase (decrease) in authorized amount | $						$ 256.2
Stock repurchase program, authorized amount | $					$ 400.0
Stock repurchase program, remaining authorized repurchase amount | $	$ 276.7		$ 276.7
Restricted Share Units
Business Organization [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares) | shares	201	466	1,784	2,235
Performance share units
Business Organization [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares) | shares	0	3	1,177	0
Luxury Brands
Business Organization [Line Items]
Weighted brand mix (percent)			29.00%
Mid-line Import Brands
Business Organization [Line Items]
Weighted brand mix (percent)			41.00%
Domestic Brands
Business Organization [Line Items]
Weighted brand mix (percent)			29.00%