Summary of Comprehensive Income (Loss) and Reconciliations of Equity (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 29, 2012		Oct. 01, 2011	Sep. 29, 2012		Oct. 01, 2011
Stockholders Equity Note [Line Items]
Beginning equity balance	$ 2,700.5		$ 2,901.9	$ 2,561.1		$ 2,568.8
Stock-based compensation transactions and other	8.8		10.3	22.8		25.8
Repurchase of common stock	(50.1)		(94.2)	(172.6)		(194.2)
Dividends declared to Lear Corporation stockholders	(13.9)		(13.2)	(42.3)		(40.0)
Dividends paid to noncontrolling interests			(0.3)	(4.3)		(18.5)
Acquisition of noncontrolling interests	(17.4)			(23.6)
Transaction with affiliates						2.4
Comprehensive income:
Net income	128.1		108.1	427.1		456.5
Other comprehensive income (loss), net of tax:
Defined benefit plan adjustments	2.6		0.1	0.8		0.3
Derivative instruments and hedging activities	18.0		(51.9)	54.0		(45.0)
Foreign currency translation adjustments	25.6		(117.6)	(20.8)		(12.9)
Other comprehensive income (loss)	46.2		(169.4)	34.0		(57.6)
Comprehensive income (loss)	174.3		(61.3)	461.1		398.9
Ending equity balance	2,802.2	[1]	2,743.2	2,802.2	[1]	2,743.2
Attributable to Lear Corporation Stockholders
Stockholders Equity Note [Line Items]
Beginning equity balance	2,565.5		2,792.7	2,436.4		2,460.2
Stock-based compensation transactions and other	8.8		10.3	22.8		25.8
Repurchase of common stock	(50.1)		(94.2)	(172.6)		(194.2)
Dividends declared to Lear Corporation stockholders	(13.9)		(13.2)	(42.3)		(40.0)
Acquisition of noncontrolling interests	(9.3)			(11.5)
Comprehensive income:
Net income	121.4		100.7	400.9		434.2
Other comprehensive income (loss), net of tax:
Defined benefit plan adjustments	2.6		0.1	0.8		0.3
Derivative instruments and hedging activities	18.0		(51.9)	54.0		(45.0)
Foreign currency translation adjustments	24.4		(118.0)	(21.1)		(14.8)
Other comprehensive income (loss)	45.0		(169.8)	33.7		(59.5)
Comprehensive income (loss)	166.4		(69.1)	434.6		374.7
Ending equity balance	2,667.4		2,626.5	2,667.4		2,626.5
Non-controlling Interests
Stockholders Equity Note [Line Items]
Beginning equity balance	135.0		109.2	124.7		108.6
Dividends paid to noncontrolling interests			(0.3)	(4.3)		(18.5)
Acquisition of noncontrolling interests	(8.1)			(12.1)
Transaction with affiliates						2.4
Comprehensive income:
Net income	6.7		7.4	26.2		22.3
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	1.2		0.4	0.3		1.9
Other comprehensive income (loss)	1.2		0.4	0.3		1.9
Comprehensive income (loss)	7.9		7.8	26.5		24.2
Ending equity balance	$ 134.8		$ 116.7	$ 134.8		$ 116.7

[1] Unaudited.