Schedule of Goodwill (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Line Items]
Carrying amount at beginning of year	$ 1,688.8
Effect of currency translation	2.7
Carrying amount at end of year	1,691.5
Passive Safety
Goodwill [Line Items]
Carrying amount at beginning of year	1,397.1
Effect of currency translation	2.9
Carrying amount at end of year	1,400.0
Electronics
Goodwill [Line Items]
Carrying amount at beginning of year	291.7
Effect of currency translation	(0.2)
Carrying amount at end of year	$ 291.5