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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation Of Revenue [Line Items]
Net sales	$ 415.0	$ 528.6	$ 874.3	$ 1,008.2
Component Products
Disaggregation Of Revenue [Line Items]
Net sales	23.8	33.7	56.1	64.9
Component Products | Security Products
Disaggregation Of Revenue [Line Items]
Net sales	18.6	26.9	44.0	51.6
Component Products | Marine Components
Disaggregation Of Revenue [Line Items]
Net sales	5.2	6.8	12.1	13.3
Real Estate Management And Development
Disaggregation Of Revenue [Line Items]
Net sales	5.2	10.4	11.2	22.3
Real Estate Management And Development | Land Sales
Disaggregation Of Revenue [Line Items]
Net sales	2.7	8.4	6.2	17.9
Real Estate Management And Development | Water Delivery
Disaggregation Of Revenue [Line Items]
Net sales	2.1	1.6	4.0	3.5
Real Estate Management And Development | Utility and Other
Disaggregation Of Revenue [Line Items]
Net sales	$ 0.4	$ 0.4	$ 1.0	$ 0.9