Pre-Production Costs Related to Long-Term Supply Agreements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Apr. 03, 2021	Apr. 04, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Pre-production E&D costs for which reimbursement is contractually guaranteed by the customer	$ 66.7	$ 50.4
Pre-production tooling costs related to customer-owned tools for which reimbursement is contractually guaranteed by the customer	31.4	54.1
Cash collected related to E&D and tooling costs	$ 77.0	$ 66.8

Amount of recoverable preproduction engineering and design costs related to long term supply agreements capitalized during the reporting period.

No definition available.

Name:	lear_PreproductionEngineeringAndDevelopmentCostsRelatedToLongTermSupplyArrangementsCostsCapitalized
Namespace Prefix:	lear_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration