Consolidated Statements of Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Redeemable Non- controlling Interests	Common Stock	Additional Paid-in Capital	Common Stock Held in Treasury	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Defined Benefit Plans	Derivative Instruments and Hedge Activities	Cumulative Translation Adjustments	Lear Corporation Stockholders’ Equity	Lear Corporation Stockholders’ Equity Cumulative Effect, Period of Adoption, Adjustment	Non-controlling Interests
Balance at beginning of year at Dec. 31, 2017			$ 153.4
Comprehensive income (loss):
Net income			12.9
Other comprehensive income (loss)			(9.4)
Total comprehensive income (loss)			3.5
Dividends declared to noncontrolling interests			(9.2)
Redeemable noncontrolling interest adjustment			10.4
Balance at end of year at Dec. 31, 2018			158.1
Balance at beginning of year at Dec. 31, 2017	$ 4,292.6	$ 2.3		$ 0.7	$ 1,215.4	$ (724.1)	$ 4,171.9	$ 2.3	$ (184.0)	$ (22.9)	$ (306.5)	$ 4,150.5	$ 2.3	$ 142.1
Comprehensive income (loss):
Net income	1,233.8						1,149.8					1,149.8		84.0
Other comprehensive income (loss)	(199.2)								11.2	13.2	(216.8)	(192.4)		(6.8)
Total comprehensive income (loss)	1,034.6						1,149.8		11.2	13.2	(216.8)	957.4		77.2
Stock-based compensation	41.4				41.4							41.4
Net issuances of shares held in treasury in settlement of stock-based compensation	(47.5)				(81.5)	34.0						(47.5)
Repurchases of common stock	(705.2)					(705.2)						(705.2)
Retirement of shares held in treasury	0.0			(0.1)	(155.9)	1,170.2	(1,014.2)					0.0
Dividends declared to Lear Corporation stockholders	(185.8)						(185.8)					(185.8)
Dividends declared to noncontrolling interests	(70.0)													(70.0)
Affiliate transaction	14.0													14.0
Disposal of noncontrolling interests	(2.0)				(2.0)							(2.0)
Noncontrolling interests — other	(3.4)													(3.4)
Redeemable noncontrolling interest adjustment	(10.4)						(10.4)					(10.4)
Balance at end of year at Dec. 31, 2018	4,360.6			0.6	1,017.4	(225.1)	4,113.6		(172.8)	(9.7)	(523.3)	4,200.7		159.9
Comprehensive income (loss):
Net income			1.8
Other comprehensive income (loss)			(1.8)
Total comprehensive income (loss)			0.0
Dividends declared to noncontrolling interests			(2.7)
Redeemable noncontrolling interest adjustment			(37.0)
Balance at end of year at Dec. 31, 2019	118.4		118.4
Comprehensive income (loss):
Net income	828.9						753.6					753.6		75.3
Other comprehensive income (loss)	(68.6)								(44.8)	19.5	(41.6)	(66.9)		(1.7)
Total comprehensive income (loss)	760.3						753.6		(44.8)	19.5	(41.6)	686.7		73.6
Stock-based compensation	23.3				23.3							23.3
Net issuances of shares held in treasury in settlement of stock-based compensation	(31.3)				(71.6)	42.4	(2.1)					(31.3)
Repurchases of common stock	(380.4)					(380.4)						(380.4)
Dividends declared to Lear Corporation stockholders	(186.3)						(186.3)					(186.3)
Dividends declared to noncontrolling interests	(76.3)													(76.3)
Disposal of noncontrolling interests	(5.6)													(5.6)
Noncontrolling interests — other	(0.2)													(0.2)
Redeemable noncontrolling interest adjustment	37.0						37.0					37.0
Balance at end of year at Dec. 31, 2019	$ 4,501.1			0.6	969.1	(563.1)	4,715.8	$ (0.8)	(217.6)	9.8	(564.9)	4,349.7		151.4
Comprehensive income (loss):
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Net income			(3.5)
Other comprehensive income (loss)			7.7
Total comprehensive income (loss)			4.2
Dividends declared to noncontrolling interests			(26.8)
Acquisition of outstanding noncontrolling interests	$ 1.4		(96.9)		1.4							1.4
Redeemable noncontrolling interest adjustment			1.1
Balance at end of year at Dec. 31, 2020	0.0		0.0
Comprehensive income (loss):
Net income	237.4						158.5					158.5		78.9
Other comprehensive income (loss)	75.5								(59.3)	2.8	124.1	67.6		7.9
Total comprehensive income (loss)	312.9						158.5		(59.3)	2.8	124.1	226.1		86.8
Stock-based compensation	40.0				40.0							40.0
Net issuances of shares held in treasury in settlement of stock-based compensation	(15.9)				(46.9)	34.5	(3.5)					(15.9)
Repurchases of common stock	(70.0)					(70.0)						(70.0)
Dividends declared to Lear Corporation stockholders	(62.1)						(62.1)					(62.1)
Dividends declared to noncontrolling interests	(90.6)													(90.6)
Acquisition of outstanding noncontrolling interests	1.4		$ (96.9)		1.4							1.4
Redeemable noncontrolling interest adjustment	(1.1)						(1.1)					(1.1)
Balance at end of year at Dec. 31, 2020	$ 4,614.9	$ (0.8)		$ 0.6	$ 963.6	$ (598.6)	$ 4,806.8		$ (276.9)	$ 12.6	$ (440.8)	$ 4,467.3	$ (0.8)	$ 147.6