Long-Term Assets - Investment in Affiliates (Details) - USD ($) $ in Millions	Mar. 31, 2018	[1]	Jan. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 1,464.7			$ 1,401.3
Lear FAWSN
Business Acquisition [Line Items]
Property, plant and equipment			$ 10.5
Other assets and liabilities assumed, net			7.2
Goodwill			21.4
Intangible assets			7.5
Preliminary purchase price allocation			$ 46.6

[1] Unaudited.