Investment in Affiliates and Other Assets - Investment in Affiliates and Other Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Other Noncurrent Assets [Line Items]
Investment in affiliates	$ 81.4	$ 89.0
Other assets:
Land held for development	161.5	165.1
Restricted cash	17.7	13.9
Deferred financing costs	6.3	6.9
IBNR receivables	7.0	6.8
Capital lease deposit	6.2	6.2
Intangible assets	5.1	5.1
Other	13.7	25.7
Total	266.8	282.9
Capitalized Operating Permits
Other assets:
Waste disposal site operating permits, net	49.3	53.2
LPC
Other Noncurrent Assets [Line Items]
Investment in affiliates	$ 81.4	$ 89.0