INCOME TAXES AND RELATED PAYMENTS - Additional Information (Detail) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) company	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Income Tax Disclosure [Abstract]
Number of wholly-owned subsidiaries (in company) | company			2
Income tax expense related to Tax Act	$ 33.2
Income tax expense related to Tax Act, deferred tax assets	178.2
Income tax benefit related to Tax Act, tax receivable liability	$ 145.1				$ 145.1
Total reserve			$ 0.2
Unrecognized tax benefits that would impact tax rate			0.1
Income tax penalties and interest accrued			0.1	$ 1.9
Income tax penalties and interest expenses			$ 0.2	1.2	0.1
Income Tax Contingency [Line Items]
Percentage of cash savings (as a percent)			85.00%
Payments to unitholders under tax receivable agreement			$ 10.0	$ 20.7	$ 20.0
Forecast
Income Tax Contingency [Line Items]
Decrease resulting from settlements with taxing authorities		$ 0.2