Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Percentage of voting equity interests acquired at the acquisition date in the business combination.

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Investments in Affiliates and Other Related Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended			3 Months Ended		12 Months Ended
	Jul. 31, 2019	Jan. 31, 2018	Sep. 30, 2017	Sep. 28, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Gain from deconsolidation	$ 4.0			$ 4.0
Redeemable noncontrolling interest						$ 118.4	$ 158.1
Noncontrolling interest, change in redemption value						37.0	(10.4)	$ (25.5)
Lear FAWSN
Related Party Transaction [Line Items]
Equity interest acquired		20.00%
Intangible assets acquired, weighted average useful life		10 years
Fair value of previously held equity interest in acquiree		$ 23.0				23.0
Noncontrolling interests, fair value		14.0
Consolidation of affiliate, revaluation gain		$ 10.0			$ 10.0
Lear STEC
Related Party Transaction [Line Items]
Intangible assets acquired, weighted average useful life			12 years
Fair value of previously held equity interest in acquiree			$ 94.0
Noncontrolling interests, fair value			125.0
Consolidation of affiliate, revaluation gain			$ 54.2
Redeemable noncontrolling interest						118.4	158.1
Noncontrolling interest, change in redemption value						$ (37.0)	$ 10.4
Lear STEC \| Lear STEC
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners			45.00%