Investments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Ownership interest held	50.00%
Total assets of variable interest entities	$ 19,634.8	$ 16,334.0	$ 14,909.7
Total liabilities of variable interest entities	14,419.3	11,764.3
Chem-Mod Clean-Coal Venture [Member]
Schedule of Equity Method Investments [Line Items]
Total revenues of limited liability companies	81.9	73.7
Total expenses of limited liability companies	17.5	4.1
Chem-Mod Clean-Coal Venture [Member] | VIE [Member]
Schedule of Equity Method Investments [Line Items]
Total assets of variable interest entities	16.3	14.0
Total liabilities of variable interest entities	$ 2.8	$ 1.4
Chem-Mod Clean-Coal Venture - U.S. and Canadian Operations [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest held	46.50%
Chem-Mod International LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest held	31.50%
C-Quest Technology LLC and C-Quest Technologies International LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest held	12.00%