Revenue Recognition - Schedule of Disaggregates of Net Sales of our Component Products and Real Estate Management and Development Segments (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Net sales	$ 510.2	$ 481.8	$ 976.2	$ 887.1
Component Products
Disaggregation Of Revenue [Line Items]
Net sales	32.4	30.1	60.8	60.0
Component Products | Security Products
Disaggregation Of Revenue [Line Items]
Net sales	27.2	26.1	51.3	52.1
Component Products | Marine Components
Disaggregation Of Revenue [Line Items]
Net sales	5.2	4.0	9.5	7.9
Real Estate Management And Development
Disaggregation Of Revenue [Line Items]
Net sales	6.0	10.3	13.2	15.9
Real Estate Management And Development | Land Sales
Disaggregation Of Revenue [Line Items]
Net sales	3.8	8.4	9.6	12.1
Real Estate Management And Development | Water Delivery
Disaggregation Of Revenue [Line Items]
Net sales	1.9	1.4	2.8	2.7
Real Estate Management And Development | Utility and Other
Disaggregation Of Revenue [Line Items]
Net sales	$ 0.3	$ 0.5	$ 0.8	$ 1.1