Recent Accounting Pronouncements - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings (deficit)		$ 67.3		$ (17.9)
Accounting Standards Update 2014-09 | Real Estate Management And Development
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Receivable	$ 6.1
Contract asset	8.8
Offsetting liability for deferred revenue	8.8
Land sales revenue		$ 0.4
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | Real Estate Management And Development
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings (deficit)	6.1
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | Non-controlling interest | Real Estate Management And Development
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings (deficit)	$ 2.7
ASU 2017-07 | Cost of Sales
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Reclassification adjustment to other components of net periodic pension and OPEB cost			$ 2.6
ASU 2017-07 | Selling, General and Administrative Expenses
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Reclassification adjustment to other components of net periodic pension and OPEB cost			$ 1.7