Segment Information Segment Assets (Detail) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		$ 8,585.2	$ 8,234.4
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		7,878.4	7,352.5
Operating Segments | Passive Safety
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		6,092.9	5,637.0
Operating Segments | Electronics
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		1,785.5	1,715.5
Corporate and other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	[1]	$ 706.8	$ 881.9

[1] Corporate and other assets mainly consist of cash and cash equivalents, income taxes and equity method investments.