Comprehensive Income and Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended		3 Months Ended		6 Months Ended		42 Months Ended
	Mar. 31, 2014	Apr. 25, 2013	Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014
Stockholders Equity Note [Line Items]
Defined benefit plan adjustments, pension and other postretirement benefit plans			$ 0.1	$ 2.6	$ 0.1	$ 5.2
Derivative instruments and hedging activities, reclassified from accumulated other comprehensive income (loss)			(3.5)	10.6	(4.5)	18.8
Accelerated stock repurchase agreement amount		800
Amount paid in accelerated stock repurchase agreement			855.5	800.0	855.5	800.0	855.5
Common stock, repurchased					1,152,832
Percentage of treasury stock repurchased				80.00%
Value of common stock repurchased, per share				$ 53.95
Common stock, additional shares repurchased	658,903
Additional amount paid in accelerated stock repurchase agreement			55.5		55.5
Value of common stock repurchased, average price per share			$ 72.11
Common stock, share repurchase program amount					594.0
Common stock repurchased, average price per share					$ 87.16
Payments for repurchases of outstanding common stock					156.0	1,000.1	1,700.0
Cash dividends declared per share					$ 0.20	$ 0.17
Dividends declared to Lear Corporation stockholders			16.7	14.1	33.9	30.6
Dividends paid to Lear Corporation stockholders					33.6	29.6
Open Market Repurchases
Stockholders Equity Note [Line Items]
Payments for repurchases of outstanding common stock					$ 100.5
Accelerated Share Repurchase Agreement
Stockholders Equity Note [Line Items]
Common stock, repurchased				11,862,836