Summary of Information Used to Compute Diluted Net Income Per Share (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 29, 2013	Jun. 30, 2012	Jun. 29, 2013	Jun. 30, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Lear	$ 137.3	$ 145.4	$ 245.8	$ 279.5
Average common shares outstanding	84,517,205	99,127,883	89,609,759	99,721,827
Dilutive effect of common stock equivalents	1,033,769	1,483,916	1,043,946	1,548,999
Average diluted shares outstanding	85,550,974	100,611,799	90,653,705	101,270,826
Basic net income per share attributable to Lear	$ 1.62	$ 1.47	$ 2.74	$ 2.80
Diluted net income per share attributable to Lear	$ 1.60	$ 1.45	$ 2.71	$ 2.76