Segment Information Net Sales Including Intersegment Sales (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales		$ 2,812.8	$ 2,608.1
Passive Safety
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	[1]	2,240.7	2,041.4
Electronics
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	[1]	572.1	566.7
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales		2,831.5	2,623.5
Operating Segments | Passive Safety
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales		2,237.9	2,040.2
Operating Segments | Electronics
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales		593.6	583.3
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales		4.0	1.4
Intersegment Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales		$ (22.7)	$ (16.8)

[1] Excluding intersegment sales.