Segment Information Income Before Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment operating income	$ 191.1	$ 157.8	$ 609.0	$ 446.5
Interest and other non-operating expenses, net	(6.5)	(6.6)	(34.4)	(39.2)
Income from equity method investments	0.5	0.6	1.2	3.5
Income before income taxes	185.1	151.8	575.8	410.8
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment operating income	195.8	157.2	620.9	436.9
Operating Segments | Passive Safety
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment operating income	190.8	145.8	589.2	404.7
Operating Segments | Electronics
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment operating income	5.0	11.4	31.7	32.2
Corporate and other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment operating income	$ (4.7)	$ 0.6	$ (11.9)	$ 9.6