Summary of Significant Accounting Policies - Summary of Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Roll Forward]
Beginning balance	$ 1,053.8	$ 726.2
Foreign currency translation and other	(16.0)	(43.1)
Ending balance	1,121.3	1,053.8
Other acquisitions
Goodwill [Roll Forward]
Acquisitions	74.6	370.7
Beijing BAI Lear Automotive Systems Co., Ltd.
Goodwill [Roll Forward]
Acquisitions	8.9
Operating segments | Seating
Goodwill [Roll Forward]
Beginning balance	1,026.8	726.2
Foreign currency translation and other	(16.5)	(43.1)
Ending balance	1,091.2	1,026.8
Operating segments | Seating | Other acquisitions
Goodwill [Roll Forward]
Acquisitions	72.0	343.7
Operating segments | Seating | Beijing BAI Lear Automotive Systems Co., Ltd.
Goodwill [Roll Forward]
Acquisitions	8.9
Operating segments | E-Systems
Goodwill [Roll Forward]
Beginning balance	27.0	0.0
Foreign currency translation and other	0.5	0.0
Ending balance	30.1	27.0
Operating segments | E-Systems | Other acquisitions
Goodwill [Roll Forward]
Acquisitions	2.6	$ 27.0
Operating segments | E-Systems | Beijing BAI Lear Automotive Systems Co., Ltd.
Goodwill [Roll Forward]
Acquisitions	$ 0.0