Segment Results - Schedule of Operating Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information, Profit (Loss) [Abstract]
Total operating revenue	$ 80.8	$ 129.4
Gain (loss) on the sale of commercial real estate properties	0.5	0.0
Interest expense	(7.8)	(9.1)
Income (Loss) from Continuing Operations Before Income Taxes	5.8	8.4
Commercial Real Estate
Segment Reporting Information, Profit (Loss) [Abstract]
Commercial Real Estate	43.4	36.8
Land Operations
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues	11.5	49.0
Materials & Construction
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues	25.9	43.6
Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Total operating revenue	80.8	129.4
Total operating profit (loss)	19.3	23.7
Gain (loss) on the sale of commercial real estate properties	0.5	0.0
Interest expense	(7.8)	(9.1)
Operating Segments | Commercial Real Estate
Segment Reporting Information, Profit (Loss) [Abstract]
Commercial Real Estate	43.4	36.8
Total operating profit (loss)	18.1	15.6
Operating Segments | Land Operations
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues	11.5	49.0
Total operating profit (loss)	5.0	12.6
Operating Segments | Materials & Construction
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues	25.9	43.6
Total operating profit (loss)	(3.8)	(4.5)
Other
Segment Reporting Information, Profit (Loss) [Abstract]
General corporate expenses	$ (6.2)	$ (6.2)