Quarterly Financial Data (unaudited) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 4,724.6	$ 4,330.3	$ 4,635.1	$ 4,521.4	$ 4,549.7	$ 4,232.7	$ 4,585.1	$ 4,359.8	$ 18,211.4	$ 17,727.3	$ 16,234.0
Gross profit	490.7	453.2	450.2	425.7	392.0	361.2	379.1	360.5
Consolidated net income	252.9	193.3	192.9	156.7	268.0	147.9	157.8	128.6	795.8	702.3	455.8
Net income attributable to Lear	$ 235.3	$ 181.0	$ 181.9	$ 147.3	$ 261.8	$ 140.1	$ 148.5	$ 122.0	$ 745.5	$ 672.4	$ 431.4
Basic net income per share attributable to Lear (in dollars per share)	$ 3.13	$ 2.37	$ 2.35	$ 1.88	$ 3.32	$ 1.75	$ 1.84	$ 1.50	$ 9.71	$ 8.39	$ 5.07
Diluted net income per share attributable to Lear (in dollars per share)	$ 3.07	$ 2.34	$ 2.33	$ 1.86	$ 3.24	$ 1.72	$ 1.81	$ 1.47	$ 9.59	$ 8.23	$ 4.99

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Aggregate revenue during the period from the sale of goods in the normal course of business, after deducting returns, allowances and discounts.

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