Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018		Apr. 01, 2017	Dec. 31, 2017
Income Tax Contingency [Line Items]
Tax benefit adjustment to the provisional income tax expense	$ 1.3
Retained earnings	4,474.8	[1]		$ 4,171.9
Tax benefits			$ 19.1
Tax benefits, release of valuation allowances with respect to deferred tax assets of certain foreign subsidiaries	35.1
Tax benefits, share-based compensation	10.1		15.5
Tax benefits, restructuring charges and various other items	4.1		$ 3.6
Tax expense related to an increase in foreign withholding tax	$ 22.0
U.S. federal statutory income tax rate	21.00%		35.00%
Accounting Standards Update 2016-16
Income Tax Contingency [Line Items]
Deferred tax asset as a result of ASU adoption				2.3
Retained earnings				$ 2.3
Other Income And Expense | Lear FAWSN
Income Tax Contingency [Line Items]
Consolidation of affiliate, revaluation gain	$ 10.0

[1] Unaudited.