Supplemental Guarantor Condensed Consolidating Financial Statements - Balance Sheets (Detail) (USD $) In Millions, unless otherwise specified	Sep. 27, 2014		Jun. 28, 2014	Dec. 31, 2013		Sep. 28, 2013	Jun. 29, 2013	Dec. 31, 2012
CURRENT ASSETS:
Cash and cash equivalents	$ 872.7	[1]		$ 1,137.7		$ 884.0		$ 1,402.2
Accounts receivable	2,843.0	[1]		2,278.3
Inventories	899.1	[1]		818.7
Other	718.2	[1]		687.8
Total current assets	5,333.0	[1]		4,922.5
LONG-TERM ASSETS:
Property, plant and equipment, net	1,614.4	[1]		1,587.2
Goodwill	740.2	[1]		757.2
Investments in subsidiaries	0			0
Intercompany accounts, net	0			0
Other	1,003.6	[1]		1,064.0
Total long-term assets	3,358.2	[1]		3,408.4
Total assets	8,691.2	[1]		8,330.9		8,464.2
CURRENT LIABILITIES:
Accounts payable and drafts	2,614.6	[1]		2,438.7
Accrued liabilities	1,336.3	[1]		1,140.4
Total current liabilities	3,950.9	[1]		3,579.1
LONG-TERM LIABILITIES:
Long-term debt	1,068.7			1,057.1
Intercompany accounts, net	0			0
Other	515.8	[1]		545.2
Total long-term liabilities	1,584.5	[1]		1,602.3
EQUITY:
Lear Corporation stockholders’ equity	3,081.9	[1]	3,145.8	3,045.9		2,813.5	2,669.3	3,487.1
Noncontrolling interests	73.9	[1]	75.4	103.6	[1]	106.5	121.0	125.1
Equity	3,155.8	[1]	3,221.2	3,149.5		2,920.0	2,790.3	3,612.2
Total liabilities and equity	8,691.2	[1]		8,330.9
Parent company
CURRENT ASSETS:
Cash and cash equivalents	291.7			343.5		210.8		481.4
Accounts receivable	70.1			41.2
Inventories	2.8			4.8
Other	158.1			147.7
Total current assets	522.7			537.2
LONG-TERM ASSETS:
Property, plant and equipment, net	94.7			95.5
Goodwill	23.5			23.5
Investments in subsidiaries	1,840.2			1,802.4
Intercompany accounts, net	1,394.2			1,373.1
Other	596.7			591.5
Total long-term assets	3,949.3			3,886.0
Total assets	4,472.0			4,423.2
CURRENT LIABILITIES:
Accounts payable and drafts	93.8			73.8
Accrued liabilities	110.1			127.9
Total current liabilities	203.9			201.7
LONG-TERM LIABILITIES:
Long-term debt	1,068.7			1,057.1
Intercompany accounts, net	0			0
Other	117.5			118.5
Total long-term liabilities	1,186.2			1,175.6
EQUITY:
Lear Corporation stockholders’ equity	3,081.9			3,045.9
Noncontrolling interests	0			0
Equity	3,081.9			3,045.9
Total liabilities and equity	4,472.0			4,423.2
Guarantor subsidiaries
CURRENT ASSETS:
Cash and cash equivalents	0.1			0.1		0.1		0.1
Accounts receivable	635.0			349.7
Inventories	343.5			297.9
Other	64.9			77.3
Total current assets	1,043.5			725.0
LONG-TERM ASSETS:
Property, plant and equipment, net	321.7			316.0
Goodwill	401.0			401.0
Investments in subsidiaries	1,891.2			1,878.5
Intercompany accounts, net				0
Other	56.4			71.5
Total long-term assets	2,670.3			2,667.0
Total assets	3,713.8			3,392.0
CURRENT LIABILITIES:
Accounts payable and drafts	742.2			582.4
Accrued liabilities	205.4			156.1
Total current liabilities	947.6			738.5
LONG-TERM LIABILITIES:
Long-term debt	0			0
Intercompany accounts, net	762.2			515.2
Other	142.1			143.0
Total long-term liabilities	904.3			658.2
EQUITY:
Lear Corporation stockholders’ equity	1,861.9			1,995.3
Noncontrolling interests	0			0
Equity	1,861.9			1,995.3
Total liabilities and equity	3,713.8			3,392.0
Non-guarantor subsidiaries
CURRENT ASSETS:
Cash and cash equivalents	580.9			794.1		673.1		920.7
Accounts receivable	2,137.9			1,887.4
Inventories	552.8			516.0
Other	495.2			462.8
Total current assets	3,766.8			3,660.3
LONG-TERM ASSETS:
Property, plant and equipment, net	1,198.0			1,175.7
Goodwill	315.7			332.7
Investments in subsidiaries				0
Intercompany accounts, net				0
Other	350.5			401.0
Total long-term assets	1,864.2			1,909.4
Total assets	5,631.0			5,569.7
CURRENT LIABILITIES:
Accounts payable and drafts	1,778.6			1,782.5
Accrued liabilities	1,020.8			856.4
Total current liabilities	2,799.4			2,638.9
LONG-TERM LIABILITIES:
Long-term debt	0			0
Intercompany accounts, net	632.0			857.9
Other	256.2			283.7
Total long-term liabilities	888.2			1,141.6
EQUITY:
Lear Corporation stockholders’ equity	1,869.5			1,685.6
Noncontrolling interests	73.9			103.6
Equity	1,943.4			1,789.2
Total liabilities and equity	5,631.0			5,569.7
Consolidation, eliminations
CURRENT ASSETS:
Cash and cash equivalents	0			0		0		0
Accounts receivable	0			0
Inventories	0			0
Other	0			0
Total current assets	0			0
LONG-TERM ASSETS:
Property, plant and equipment, net	0			0
Goodwill	0			0
Investments in subsidiaries	(3,731.4)			(3,680.9)
Intercompany accounts, net	(1,394.2)			(1,373.1)
Other	0			0
Total long-term assets	(5,125.6)			(5,054.0)
Total assets	(5,125.6)			(5,054.0)
CURRENT LIABILITIES:
Accounts payable and drafts	0			0
Accrued liabilities	0			0
Total current liabilities	0			0
LONG-TERM LIABILITIES:
Long-term debt	0			0
Intercompany accounts, net	(1,394.2)			(1,373.1)
Other	0			0
Total long-term liabilities	(1,394.2)			(1,373.1)
EQUITY:
Lear Corporation stockholders’ equity	(3,731.4)			(3,680.9)
Noncontrolling interests	0			0
Equity	(3,731.4)			(3,680.9)
Total liabilities and equity	$ (5,125.6)			$ (5,054.0)

[1] (1) Unaudited.