ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Increase (Decrease) in AOCI
Beginning balance	$ 2,974.3	$ 2,674.4	$ 2,237.5
Other comprehensive income (loss) before reclassifications:
Pre-tax	48.7	9.1	37.3
Tax effect	1.5	(6.7)	(3.3)
Amounts reclassified from accumulated other comprehensive income (loss):
Provision for income taxes	6.3	9.0	8.9
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX	30.0	(26.5)	5.7
Ending balance	2,789.1	2,974.3	2,674.4
Interest Rate Derivative Instruments
Amounts reclassified from accumulated other comprehensive income (loss):
Pre-tax		(0.2)	(4.0)
Floorplan interest expense (pre-tax)
Amounts reclassified from accumulated other comprehensive income (loss):
Pre-tax	(15.7)	(20.6)	(15.4)
Other interest expense, net (pre-tax)
Amounts reclassified from accumulated other comprehensive income (loss):
Pre-tax	(10.8)	(17.0)	(17.9)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in AOCI
Beginning balance	1.6	28.1	22.5
Amounts reclassified from accumulated other comprehensive income (loss):
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX	30.0	(26.5)	5.7
Ending balance	31.6	1.6	28.1
Accumulated Income (Loss) on Foreign Currency Translation
Increase (Decrease) in AOCI
Beginning balance	(56.5)	(37.4)	(61.1)
Other comprehensive income (loss) before reclassifications:
Pre-tax	54.8	(19.1)	23.7
Tax effect	0.0	0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss):
Provision for income taxes	0.0	0.0	0.0
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX	54.8	(19.1)	23.7
Ending balance	(1.7)	(56.5)	(37.4)
Accumulated Income (Loss) on Foreign Currency Translation \| Interest Rate Derivative Instruments
Amounts reclassified from accumulated other comprehensive income (loss):
Pre-tax		0.0	0.0
Accumulated Income (Loss) on Foreign Currency Translation \| Floorplan interest expense (pre-tax)
Amounts reclassified from accumulated other comprehensive income (loss):
Pre-tax	0.0	0.0	0.0
Accumulated Income (Loss) on Foreign Currency Translation \| Other interest expense, net (pre-tax)
Amounts reclassified from accumulated other comprehensive income (loss):
Pre-tax	0.0	0.0	0.0
Accumulated Income (Loss) on Interest Rate Swaps
Increase (Decrease) in AOCI
Beginning balance	58.2	65.6	83.6
Other comprehensive income (loss) before reclassifications:
Pre-tax	(6.1)	28.2	13.7
Tax effect	1.5	(6.7)	(3.3)
Amounts reclassified from accumulated other comprehensive income (loss):
Provision for income taxes	6.3	9.0	8.9
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX	(24.9)	(7.4)	(18.0)
Ending balance	33.3	58.2	65.6
Accumulated Income (Loss) on Interest Rate Swaps \| Interest Rate Derivative Instruments
Amounts reclassified from accumulated other comprehensive income (loss):
Pre-tax		(0.2)	(4.0)
Accumulated Income (Loss) on Interest Rate Swaps \| Floorplan interest expense (pre-tax)
Amounts reclassified from accumulated other comprehensive income (loss):
Pre-tax	(15.7)	(20.6)	(15.4)
Accumulated Income (Loss) on Interest Rate Swaps \| Other interest expense, net (pre-tax)
Amounts reclassified from accumulated other comprehensive income (loss):
Pre-tax	$ (10.8)	$ (17.0)	$ (17.9)

GROUP 1 AUTOMOTIVE INC 10-K