Other Noncurrent Assets - Other Noncurrent Assets (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Other noncurrent assets:
Land held for development	$ 157.4	$ 157.2
Restricted cash	20.9	19.6
IBNR receivables	7.1	7.0
Capital lease deposit	6.2	6.2
Intangible assets		5.1
Pension asset	1.9	1.7
Other	11.7	11.8
Total	252.4	256.7
Capitalized Operating Permits
Other noncurrent assets:
Waste disposal site operating permits, net	$ 47.2	$ 48.1