ACQUISITIONS - Pro Forma Summary of All Acquisitions (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Business Combination and Asset Acquisition [Abstract]
Revenue	$ 8,317.4	$ 8,284.7	$ 24,560.3	$ 24,102.2
Net income attributable to Lithia Motors, Inc.	$ 266.1	$ 357.1	$ 838.6	$ 1,094.7
Basic earnings attributable to Lithia Motors, Inc. per share (in dollars per share)	$ 9.65	$ 12.96	$ 30.46	$ 38.43
Diluted earnings attributable to Lithia Motors, Inc. per share (in dollars per share)	$ 9.63	$ 12.91	$ 30.40	$ 38.29