Quarterly Financial Data (unaudited) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Dec. 31, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 4,643.5	$ 4,526.4	$ 4,724.8	$ 4,662.9	$ 4,724.6	$ 4,330.3	$ 4,635.1	$ 4,521.4	$ 18,557.6	$ 18,211.4	$ 17,727.3
Gross profit	512.1	513.9	540.4	535.7	490.7	453.2	450.2	425.7
Consolidated net income	248.5	235.0	294.5	262.5	252.9	193.3	192.9	156.7	1,040.5	795.8	702.3
Net income attributable to Lear	$ 229.9	$ 214.4	$ 282.4	$ 248.4	$ 235.3	$ 181.0	$ 181.9	$ 147.3	$ 975.1	$ 745.5	$ 672.4
Basic net income per share attributable to Lear (in dollars per share)	$ 3.28	$ 3.01	$ 3.85	$ 3.33	$ 3.13	$ 2.37	$ 2.35	$ 1.88	$ 13.48	$ 9.71	$ 8.39
Diluted net income per share attributable to Lear (in dollars per share)	$ 3.24	$ 2.98	$ 3.82	$ 3.29	$ 3.07	$ 2.34	$ 2.33	$ 1.86	$ 13.33	$ 9.59	$ 8.23