Revenue - Disaggregation of Sales - Schedule of Disaggregates of Net Sales of our Component Products and Real Estate Management and Development Segments (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Net sales	$ 458.6	$ 475.2	$ 1,332.9	$ 1,483.5
Component Products
Disaggregation Of Revenue [Line Items]
Net sales	28.4	29.7	84.5	94.6
Component Products | Security Products
Disaggregation Of Revenue [Line Items]
Net sales	21.2	23.4	65.2	75.0
Component Products | Marine Components
Disaggregation Of Revenue [Line Items]
Net sales	7.2	6.3	19.3	19.6
Real Estate Management And Development
Disaggregation Of Revenue [Line Items]
Net sales	13.3	8.1	24.5	30.5
Real Estate Management And Development | Land Sales
Disaggregation Of Revenue [Line Items]
Net sales	10.6	6.3	16.8	24.3
Real Estate Management And Development | Water Delivery
Disaggregation Of Revenue [Line Items]
Net sales	2.2	1.4	6.2	4.9
Real Estate Management And Development | Utility and Other
Disaggregation Of Revenue [Line Items]
Net sales	$ 0.5	$ 0.4	$ 1.5	$ 1.3