NET INCOME PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted average common shares outstanding - basic (in shares)	28,400	28,100	29,000	27,400
Weighted average common shares outstanding – diluted (in shares)	28,600	28,400	29,100	27,600
Basic earnings per share attributable to Lithia Motors, Inc. (in dollars per share)	$ 11.67	$ 10.83	$ 23.25	$ 16.83
Diluted earnings per share attributable to Lithia Motors, Inc. (in dollars per share)	$ 11.60	$ 10.75	$ 23.15	$ 16.69
Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Lithia Motors, Inc. and applicable to common stockholders - basic	$ 331.4		$ 673.6
Reallocation of net income due to conversion of Class B to Class A common shares outstanding	0.0
Conversion of Class B common shares into Class A common shares	0.0		0.0
Net income attributable to Lithia Motors, Inc. and applicable to common stockholders - diluted	$ 331.4		$ 673.6
Weighted average common shares outstanding - basic (in shares)	28,400		29,000
Conversion of Class B common shares into Class A common shares (in shares)	0		0
Effect of dilutive stock options on weighted average common shares (in shares)	200		100
Weighted average common shares outstanding – diluted (in shares)	28,600		29,100
Basic earnings per share attributable to Lithia Motors, Inc. (in dollars per share)	$ 11.67		$ 23.25
Diluted earnings per share attributable to Lithia Motors, Inc. (in dollars per share)	$ 11.60		$ 23.15
Class A
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Lithia Motors, Inc. and applicable to common stockholders - basic		$ 304.9		$ 460.5
Reallocation of net income due to conversion of Class B to Class A common shares outstanding		0.0
Conversion of Class B common shares into Class A common shares		0.0		0.6
Net income attributable to Lithia Motors, Inc. and applicable to common stockholders - diluted		$ 304.9		$ 461.1
Weighted average common shares outstanding - basic (in shares)		28,100		27,400
Conversion of Class B common shares into Class A common shares (in shares)		0		0
Effect of dilutive stock options on weighted average common shares (in shares)		300		200
Weighted average common shares outstanding – diluted (in shares)		28,400		27,600
Basic earnings per share attributable to Lithia Motors, Inc. (in dollars per share)		$ 10.83		$ 16.83
Diluted earnings per share attributable to Lithia Motors, Inc. (in dollars per share)		$ 10.75		$ 16.69
Class B
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Lithia Motors, Inc. and applicable to common stockholders - basic		$ 0.0		$ 0.6
Reallocation of net income due to conversion of Class B to Class A common shares outstanding		0.0
Conversion of Class B common shares into Class A common shares		0.0		0.0
Net income attributable to Lithia Motors, Inc. and applicable to common stockholders - diluted		$ 0.0		$ 0.6
Weighted average common shares outstanding - basic (in shares)		0		0
Conversion of Class B common shares into Class A common shares (in shares)		0		0
Effect of dilutive stock options on weighted average common shares (in shares)		0		0
Weighted average common shares outstanding – diluted (in shares)		0		0
Basic earnings per share attributable to Lithia Motors, Inc. (in dollars per share)		$ 0		$ 16.83
Diluted earnings per share attributable to Lithia Motors, Inc. (in dollars per share)		$ 0		$ 16.69