Segment Results - Schedule of Operating Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information, Profit (Loss) [Abstract]
Total operating revenue	$ 73.9	$ 109.1	$ 154.7	$ 238.5
Gain (loss) on the disposal of assets, net	0.0	0.0	0.5	0.0
Interest expense	(7.8)	(8.1)	(15.6)	(17.2)
Income (Loss) from Continuing Operations Before Income Taxes	(4.1)	(1.3)	1.7	7.1
Commercial Real Estate
Segment Reporting Information, Profit (Loss) [Abstract]
Commercial Real Estate	34.0	39.1	77.4	75.9
Land Operations
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues	9.8	24.9	21.3	73.9
Materials & Construction
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues	30.1	45.1	56.0	88.7
Operating Segments
Segment Reporting Information, Profit (Loss) [Abstract]
Total operating revenue	73.9	109.1	154.7	238.5
Total operating profit (loss)	6.0	13.2	25.2	36.9
Gain (loss) on the disposal of assets, net	0.0	0.0	0.5	0.0
Interest expense	(7.8)	(8.1)	(15.6)	(17.2)
Operating Segments | Commercial Real Estate
Segment Reporting Information, Profit (Loss) [Abstract]
Commercial Real Estate	34.0	39.1	77.4	75.9
Total operating profit (loss)	8.9	17.0	26.9	32.6
Operating Segments | Land Operations
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues	9.8	24.9	21.3	73.9
Total operating profit (loss)	4.7	0.5	9.7	13.1
Operating Segments | Materials & Construction
Segment Reporting Information, Profit (Loss) [Abstract]
Revenues	30.1	45.1	56.0	88.7
Total operating profit (loss)	(7.6)	(4.3)	(11.4)	(8.8)
Other
Segment Reporting Information, Profit (Loss) [Abstract]
Corporate and other expense	$ (2.3)	$ (6.4)	$ (8.4)	$ (12.6)