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								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation Of Revenue [Line Items]
Net sales	$ 388.7	$ 455.2	$ 510.2	$ 466.0	$ 495.9	$ 496.5	$ 481.7	$ 405.3	$ 1,820.1	$ 1,879.4	$ 1,519.4
Component Products
Disaggregation Of Revenue [Line Items]
Net sales									118.2	112.0	108.9
Component Products | Security Products
Disaggregation Of Revenue [Line Items]
Net sales									98.4	96.6	94.7
Component Products | Marine Components
Disaggregation Of Revenue [Line Items]
Net sales									19.8	15.4	14.2
Real Estate Management And Development
Disaggregation Of Revenue [Line Items]
Net sales									40.0	38.4	46.2
Real Estate Management And Development | Land Sales
Disaggregation Of Revenue [Line Items]
Net sales									32.3	30.2	38.3
Real Estate Management And Development | Water Delivery
Disaggregation Of Revenue [Line Items]
Net sales									5.6	6.0	6.0
Real Estate Management And Development | Utility and Other
Disaggregation Of Revenue [Line Items]
Net sales									$ 2.1	$ 2.2	$ 1.9