Summary of Significant Accounting Policies - Summary of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Beginning balance	$ 1,405.3	$ 1,401.3
Foreign currency translation and other	(10.0)	(18.4)
Ending balance	1,614.3	1,405.3
Other acquisitions
Goodwill [Roll Forward]
Balance as of December 31, 2018	219.0
Lear FAWSN
Goodwill [Roll Forward]
Affiliate transaction		22.4
Seating
Goodwill [Roll Forward]
Beginning balance	1,244.3	1,274.4
Foreign currency translation and other	(8.9)	(30.1)
Ending balance	1,235.4	1,244.3
Seating | Other acquisitions
Goodwill [Roll Forward]
Balance as of December 31, 2018	0.0
Seating | Lear FAWSN
Goodwill [Roll Forward]
Affiliate transaction		0.0
E-Systems
Goodwill [Roll Forward]
Beginning balance	161.0	126.9
Foreign currency translation and other	(1.1)	11.7
Ending balance	378.9	161.0
E-Systems | Other acquisitions
Goodwill [Roll Forward]
Balance as of December 31, 2018	$ 219.0
E-Systems | Lear FAWSN
Goodwill [Roll Forward]
Affiliate transaction		$ 22.4