Goodwill (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Roll Forward]
Balance at January 1, 2018	$ 1,401.3
Affiliate transaction	21.4
Foreign currency translation and other	42.0
Balance at March 31, 2018	1,464.7	[1]
Operating segments | Seating
Goodwill [Roll Forward]
Balance at January 1, 2018	1,274.4
Affiliate transaction	0.0
Foreign currency translation and other	19.3
Balance at March 31, 2018	1,293.7
Operating segments | E-Systems
Goodwill [Roll Forward]
Balance at January 1, 2018	126.9
Foreign currency translation and other	22.7
Balance at March 31, 2018	171.0
Operating segments | E-Systems | Lear FAWSN
Goodwill [Roll Forward]
Affiliate transaction	$ 21.4

[1] Unaudited.