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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Total revenue reported by the acquired entity for its previous full fiscal year before the business acquisition.

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This element represents the fair value of the noncontrolling interest in the acquiree at the acquisition date.

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Fair value at acquisition-date of the equity interest in the acquiree held by the acquirer, immediately before the acquisition date for businesses combined in stages.

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Change in noncontrolling interest during the period as a result of a change in the redemption value of redeemable noncontrolling interest.

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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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As of the reporting date, the aggregate carrying amount of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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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
	Jan. 31, 2018	Sep. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Redeemable noncontrolling interest				$ 153.4	$ 158.1	$ 153.4
Noncontrolling interest, change in redemption value					(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
Annual sales	$ 100.0
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			94.0
Noncontrolling interests, fair value		125.0
Consolidation of affiliate, revaluation gain		54.2		54.2
Annual sales		$ 280.0
Redeemable noncontrolling interest				$ 153.4	158.1	153.4
Noncontrolling interest, change in redemption value					$ 10.4	$ 25.5
Lear STEC \| Lear STEC
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners		45.00%