Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other long-term assets		$ 15.2	$ 15.2	$ 12.7
Impairment loss		5.0	5.0
Tax benefits (expense) related to derivative instruments and hedging activities recognized in other comprehensive income (loss)			(5.5)	(3.3)	$ (15.9)
Lear FAWSN
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Noncontrolling interests, fair value	$ 14.0
Fair value of previously held equity interest in acquiree	$ 23.0		23.0
Level 3 | Lear FAWSN
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, plant and equipment, fair value		11.0	11.0	11.0
Intangible assets		7.5	7.5	7.5
Noncontrolling interests, fair value		14.0	14.0	23.0
Foreign exchange contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount		2,462.8	2,462.8	2,153.0
Designated as hedging instrument | Foreign exchange contract | Derivative instruments and hedging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Pretax net losses related to derivative instruments and hedging activities in accumulated other comprehensive loss		19.4	19.4	1.7
Net investment hedging | Designated as hedging instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount		300.0	300.0	0.0
Net investment hedging | Designated as hedging instrument | Interest rate swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount		1.8	1.8
Cash flow hedging | Designated as hedging instrument | Interest rate swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount				500.0
Other current liabilities				14.7
Cash flow hedging | Designated as hedging instrument | Foreign exchange contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount		1,465.8	1,465.8	1,499.0
Other current liabilities		4.5	4.5	$ 8.4
Estimate of Fair Value Measurement [Member] | Level 3 | Xevo Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible assets		$ 93.2	$ 93.2