Investments in Affiliates and Other Related Party Transactions - Summarized Group Financial Information for Affiliates Accounted for under Equity Method (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity Method Investment, Summarized Financial Information [Abstract]
Current assets	$ 794.3	$ 767.1
Non-current assets	183.4	143.5
Current liabilities	627.6	548.9
Non-current liabilities	5.6	5.8
Net sales	1,802.7	1,686.5	6,240.5
Gross profit	129.3	121.9	452.6
Income (loss) before provision for income taxes	117.8	110.1	(109.0)
Net income (loss) attributable to affiliates	$ 92.9	$ 89.0	$ (76.1)

Investments in Affiliates and Other Related Party Transactions - Summarized Group Financial Information for Affiliates Accounted for under Equity Method (Detail) (USD $)
In Millions, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Equity Method Investment, Summarized Financial Information [Abstract]

Current assets

$ 794.3us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentAssets

$ 767.1us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentAssets

Non-current assets

183.4us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNoncurrentAssets

143.5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNoncurrentAssets

Current liabilities

627.6us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentLiabilities

548.9us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentLiabilities

Non-current liabilities

5.6us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNoncurrentLiabilities

5.8us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNoncurrentLiabilities

Net sales

1,802.7us-gaap_EquityMethodInvestmentSummarizedFinancialInformationRevenue

1,686.5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationRevenue

6,240.5us-gaap_EquityMethodInvestmentSummarizedFinancialInformationRevenue

Gross profit

129.3us-gaap_EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLoss

121.9us-gaap_EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLoss

452.6us-gaap_EquityMethodInvestmentSummarizedFinancialInformationGrossProfitLoss

Income (loss) before provision for income taxes

117.8lea_EquityMethodInvestmentSummarizedFinancialInformationIncomeLossBeforeIncomeTaxes

110.1lea_EquityMethodInvestmentSummarizedFinancialInformationIncomeLossBeforeIncomeTaxes

(109.0)lea_EquityMethodInvestmentSummarizedFinancialInformationIncomeLossBeforeIncomeTaxes

Net income (loss) attributable to affiliates

$ 92.9us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss

$ 89.0us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss

$ (76.1)us-gaap_EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLoss

- Definition

The amount of income (loss) from continuing operations before income tax provision reported by an equity method investment of the entity.

+ References

No definition available.

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- Definition

The amount of current assets reported by an equity method investment of the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(g))

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

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-Subparagraph (f)

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Publisher SEC

-Name Regulation S-X (SX)

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- Definition

The amount of current liabilities reported by an equity method investment of the entity.

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- Definition

The amount of gross profit (loss) reported by an equity method investment of the entity.

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- Definition

The amount of net income (loss) reported by an equity method investment of the entity.

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- Definition

The amount of noncurrent assets reported by an equity method investment of the entity.

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- Definition

The amount of noncurrent liabilities reported by an equity method investment of the entity.

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- Definition

The amount of revenue from sale of goods and services reduced by sales returns, allowances, and discounts reported by an equity method investment of the entity.

+ References

No definition available.

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