Segment Information Segment Assets (Detail) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		$ 8,878.1	$ 8,549.9
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		8,283.0	7,702.6
Operating Segments | Passive Safety
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		6,479.3	6,114.2
Operating Segments | Electronics
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		1,803.7	1,588.4
Corporate and other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	[1]	$ 595.1	$ 847.3

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