Summary of Comprehensive Income (Loss) and Reconciliations of Equity (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended				33 Months Ended
	Sep. 28, 2013		Sep. 29, 2012		Sep. 28, 2013		Sep. 29, 2012		Sep. 28, 2013
Stockholders Equity Note [Line Items]
Beginning equity balance	$ 2,790.3		$ 2,700.5		$ 3,612.2		$ 2,561.1
Stock-based compensation transactions	14.2		8.8		36.0		22.8
Repurchase of common stock			(50.1)		(1,000.1)		(172.6)		(1,500.0)
Dividends declared to Lear Corporation stockholders	(14.2)		(13.9)		(44.8)		(42.3)
Dividends paid to noncontrolling interests	(18.6)				(33.4)		(4.3)
Acquisition of noncontrolling interests			(17.4)		(6.6)		(23.6)
Comprehensive income:
Net income	116.7		128.1		375.9		427.1
Other comprehensive income (loss), net of tax:
Defined benefit plan adjustments	1.8	[1]	2.6	[2]	5.5	[1]	0.8	[2]
Derivative instruments and hedging activities	(5.3)	[3]	18.0	[4]	(14.1)	[3]	54.0	[4]
Foreign currency translation adjustments	35.1		25.6		(10.6)		(20.8)
Other comprehensive income (loss)	31.6		46.2		(19.2)		34.0
Comprehensive income	148.3		174.3		356.7		461.1
Ending equity balance	2,920.0	[5]	2,802.2		2,920.0	[5]	2,802.2		2,920.0	[5]
Parent
Stockholders Equity Note [Line Items]
Beginning equity balance	2,669.3		2,565.5		3,487.1		2,436.4
Stock-based compensation transactions	14.2		8.8		36.0		22.8
Repurchase of common stock			(50.1)		(1,000.1)		(172.6)
Dividends declared to Lear Corporation stockholders	(14.2)		(13.9)		(44.8)		(42.3)
Acquisition of noncontrolling interests			(9.3)		(3.2)		(11.5)
Comprehensive income:
Net income	112.8		121.4		358.6		400.9
Other comprehensive income (loss), net of tax:
Defined benefit plan adjustments	1.8	[1]	2.6	[2]	5.5	[1]	0.8	[2]
Derivative instruments and hedging activities	(5.3)	[3]	18.0	[4]	(14.1)	[3]	54.0	[4]
Foreign currency translation adjustments	34.9		24.4		(11.5)		(21.1)
Other comprehensive income (loss)	31.4		45.0		(20.1)		33.7
Comprehensive income	144.2		166.4		338.5		434.6
Ending equity balance	2,813.5		2,667.4		2,813.5		2,667.4		2,813.5
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Beginning equity balance	121.0		135.0		125.1		124.7
Dividends paid to noncontrolling interests	(18.6)				(33.4)		(4.3)
Acquisition of noncontrolling interests			(8.1)		(3.4)		(12.1)
Comprehensive income:
Net income	3.9		6.7		17.3		26.2
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	0.2		1.2		0.9		0.3
Other comprehensive income (loss)	0.2		1.2		0.9		0.3
Comprehensive income	4.1		7.9		18.2		26.5
Ending equity balance	$ 106.5		$ 134.8		$ 106.5		$ 134.8		$ 106.5

[1] Includes comprehensive income of $2.6 million and $7.8 million for the three and nine months ended September 28, 2013, respectively, reclassified from accumulated other comprehensive loss. See Note 8, "Pension and Other Postretirement Benefit Plans."

[2] Includes comprehensive income of $2.5 million and $8.1 million for the three and nine months ended September 29, 2012, respectively, reclassified from accumulated other comprehensive loss. See Note 8, "Pension and Other Postretirement Benefit Plans."

[3] Includes comprehensive loss of $8.3 million and $27.1 million for the three and nine months ended September 28, 2013, respectively, reclassified from accumulated other comprehensive loss. See Note 15, "Financial Instruments."

[4] Includes comprehensive income (loss) of ($0.3) million and $5.8 million for the three and nine months ended September 29, 2012, respectively, reclassified from accumulated other comprehensive loss. See Note 15, "Financial Instruments."

[5] Unaudited.