Business Combinations, Dispositions and Related Transactions - Recognition Based on Final Asset Allocation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Land held for development:
Current		$ 9.9	$ 15.0
Noncurrent		$ 157.2	$ 165.1
Basic Management Inc And Landwell
Consideration:
Cash	$ 5.3
Total fair value of consideration	32.6
Fair value of our existing equity interest in BMI and LandWell	43.4
Bargain purchase gain recognized	28.0
Total	104.0
Allocation of purchase price to identifiable assets acquired and liabilities assumed:
Cash	27.4
Land held for development:
Current	14.3
Noncurrent	158.1
Other current assets	9.4
Property, plant and equipment	29.0
Intangible asset	5.1
Other noncurrent assets	3.4
Long-term debt	(14.3)
Other liabilities	(66.9)
Total net identifiable assets	165.5
Noncontrolling interest in BMI and LandWell	(61.5)
Total	104.0
Basic Management Inc And Landwell | Deferred Payment | Present Value
Consideration:
Business combination consideration - liability incurred	8.2
Basic Management Inc And Landwell | Promissory Note
Consideration:
Business combination consideration - liability incurred	$ 19.1