Supplemental Guarantor Condensed Consolidating Financial Statements - Income Statement (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Sep. 27, 2014	Sep. 28, 2013
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 4,232.7	$ 3,917.7	$ 13,177.6	$ 11,977.9
Cost of sales	3,871.5	3,587.5	12,076.8	10,997.6
Selling, general and administrative expenses	128.1	128.6	402.8	386.1
Intercompany operating (income) expense, net	0	0	0	0
Amortization of intangible assets	8.6	8.6	25.4	25.8
Interest expense	15.7	17.5	47.1	51.6
Other expense, net	11.1	16.8	57.1	37.8
Consolidated income before provision for income taxes and equity in net income of affiliates	197.7	158.7	568.4	479.0
Provision for income taxes	57.6	51.2	163.1	130.2
Equity in net income of affiliates	(7.8)	(9.2)	(29.0)	(27.1)
Equity in net income of subsidiaries	0	0	0	0
Consolidated net income	147.9	116.7	434.3	375.9
Less: Net income attributable to noncontrolling interests	7.8	3.9	23.7	17.3
Net income attributable to Lear	140.1	112.8	410.6	358.6
Consolidated comprehensive income	50.9	148.3	332.2	356.7
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	9.2	4.1	23.0	18.2
Comprehensive income attributable to Lear	41.7	144.2	309.2	338.5
Parent company
Condensed Financial Statements, Captions [Line Items]
Net sales	120.5	105.2	351.3	352.4
Cost of sales	147.8	132.6	443.2	429.9
Selling, general and administrative expenses	35.0	43.0	125.9	121.7
Intercompany operating (income) expense, net	(52.5)	(45.5)	(241.0)	(169.9)
Amortization of intangible assets	0.5	0.5	1.3	1.3
Interest expense	10.6	11.9	34.8	36.0
Other expense, net	0.9	0.6	20.8	6.8
Consolidated income before provision for income taxes and equity in net income of affiliates	(21.8)	(37.9)	(33.7)	(73.4)
Provision for income taxes	(8.1)	(11.2)	(13.4)	(23.6)
Equity in net income of affiliates	0.1	(0.1)	0.7	(0.8)
Equity in net income of subsidiaries	(153.9)	(139.4)	(431.6)	(407.6)
Consolidated net income	140.1	112.8	410.6	358.6
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Lear	140.1	112.8	410.6	358.6
Consolidated comprehensive income	41.7	144.2	309.2	338.5
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	0	0	0	0
Comprehensive income attributable to Lear	41.7	144.2	309.2	338.5
Guarantor subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	1,802.7	1,557.8	5,252.5	4,701.3
Cost of sales	1,660.7	1,411.2	4,842.8	4,277.4
Selling, general and administrative expenses	26.9	17.3	71.4	49.2
Intercompany operating (income) expense, net	42.6	33.6	122.2	98.0
Amortization of intangible assets	1.2	1.2	3.6	3.6
Interest expense	6.6	6.0	17.8	18.1
Other expense, net	0.4	0.2	0.8	1.0
Consolidated income before provision for income taxes and equity in net income of affiliates	64.3	88.3	193.9	254.0
Provision for income taxes	27.0	31.7	80.1	92.3
Equity in net income of affiliates	(0.5)	(0.3)	(1.0)	(0.4)
Equity in net income of subsidiaries	(84.8)	(37.0)	(217.8)	(122.9)
Consolidated net income	122.6	93.9	332.6	285.0
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Lear	122.6	93.9	332.6	285.0
Consolidated comprehensive income	113.9	88.9	328.9	273.0
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	0	0	0	0
Comprehensive income attributable to Lear	113.9	88.9	328.9	273.0
Non-guarantor subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	3,503.3	3,351.6	11,189.0	10,326.7
Cost of sales	3,256.8	3,140.6	10,406.0	9,692.8
Selling, general and administrative expenses	66.2	68.3	205.5	215.2
Intercompany operating (income) expense, net	9.9	11.9	118.8	71.9
Amortization of intangible assets	6.9	6.9	20.5	20.9
Interest expense	(1.5)	(0.4)	(5.5)	(2.5)
Other expense, net	9.8	16.0	35.5	30.0
Consolidated income before provision for income taxes and equity in net income of affiliates	155.2	108.3	408.2	298.4
Provision for income taxes	38.7	30.7	96.4	61.5
Equity in net income of affiliates	(7.4)	(8.8)	(28.7)	(25.9)
Equity in net income of subsidiaries	0	0	0	0
Consolidated net income	123.9	86.4	340.5	262.8
Less: Net income attributable to noncontrolling interests	7.8	3.9	23.7	17.3
Net income attributable to Lear	116.1	82.5	316.8	245.5
Consolidated comprehensive income	35.5	122.8	241.9	254.7
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	9.2	4.1	23.0	18.2
Comprehensive income attributable to Lear	26.3	118.7	218.9	236.5
Consolidation, eliminations
Condensed Financial Statements, Captions [Line Items]
Net sales	(1,193.8)	(1,096.9)	(3,615.2)	(3,402.5)
Cost of sales	(1,193.8)	(1,096.9)	(3,615.2)	(3,402.5)
Selling, general and administrative expenses	0	0	0	0
Intercompany operating (income) expense, net	0	0	0	0
Amortization of intangible assets	0	0	0	0
Interest expense	0	0	0	0
Other expense, net	0	0	0	0
Consolidated income before provision for income taxes and equity in net income of affiliates	0	0	0	0
Provision for income taxes	0	0	0	0
Equity in net income of affiliates	0	0	0	0
Equity in net income of subsidiaries	238.7	176.4	649.4	530.5
Consolidated net income	(238.7)	(176.4)	(649.4)	(530.5)
Less: Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Lear	(238.7)	(176.4)	(649.4)	(530.5)
Consolidated comprehensive income	(140.2)	(207.6)	(547.8)	(509.5)
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	0	0	0	0
Comprehensive income attributable to Lear	$ (140.2)	$ (207.6)	$ (547.8)	$ (509.5)