Other Current Assets - Summary of Major Classes of Other Current Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Premium finance advances and loans	$ 220.2	$ 232.6
Accrued supplemental, direct bill and other receivables	181.1	156.3
Refined coal production related receivables	108.1	103.5
Deferred income taxes - current	120.8	102.2
Prepaid expenses	79.1	72.1
Total other current assets	$ 709.3	$ 666.7