Net Income Per Share Attributable to Lear (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Apr. 02, 2022	Apr. 03, 2021
Earnings Per Share [Abstract]
Net income attributable to Lear	$ 49.4	$ 203.7
Average common shares outstanding (in shares)	59,932,030	60,312,573
Dilutive effect of common stock equivalents (in shares)	278,949	248,286
Average diluted shares outstanding (in shares)	60,210,979	60,560,859
Basic net income per share attributable to Lear (in dollars per share)	$ 0.82	$ 3.38
Diluted net income per share attributable to Lear (in dollars per share)	$ 0.82	$ 3.36