CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 03, 2021	Jul. 04, 2020	Jul. 03, 2021	Jul. 04, 2020
Income Statement [Abstract]
Net sales	$ 4,760.7	$ 2,444.5	$ 10,115.1	$ 6,902.2
Cost of sales	4,359.3	2,571.9	9,220.9	6,695.4
Selling, general and administrative expenses	170.8	150.9	339.7	294.6
Amortization of intangible assets	25.1	16.0	41.6	33.1
Interest expense	22.3	27.2	44.6	51.6
Other (income) expense, net	(46.1)	(3.2)	(39.8)	37.3
Consolidated income (loss) before provision (benefit) for income taxes and equity in net income of affiliates	229.3	(318.3)	508.1	(209.8)
Provision (benefit) for income taxes	39.3	(41.0)	98.2	(14.5)
Equity in net income of affiliates	(4.9)	(7.8)	(10.8)	(9.4)
Consolidated net income (loss)	194.9	(269.5)	420.7	(185.9)
Less: Net income attributable to noncontrolling interests	19.7	24.4	41.8	31.6
Net income (loss) attributable to Lear	$ 175.2	$ (293.9)	$ 378.9	$ (217.5)
Basic net income (loss) per share available to Lear common stockholders (in dollars per share)	$ 2.91	$ (4.89)	$ 6.28	$ (3.61)
Diluted net income (loss) per share available to Lear common stockholders (in dollars per share)	2.89	(4.89)	6.25	(3.61)
Cash dividends declared per share (in dollars per share)	$ 0.25	$ 0	$ 0.50	$ 0.77
Average common shares outstanding (in shares)	60,292,000	60,102,925	60,302,398	60,310,559
Average diluted shares outstanding (in shares)	60,611,505	60,102,925	60,585,907	60,310,559
Consolidated comprehensive income (loss) (Condensed Consolidated Statements of Equity)	$ 259.4	$ (142.1)	$ 398.8	$ (339.9)
Less: Comprehensive income attributable to noncontrolling interests	21.6	25.5	42.6	27.9
Comprehensive income (loss) attributable to Lear	$ 237.8	$ (167.6)	$ 356.2	$ (367.8)