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Derivative Instruments and Hedging Activities - Summary of Fair Value of Derivative Instruments Recorded in Combined Consolidated Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total derivatives	$ (4.1)		$ 6.5
Derivatives Designated as Hedging Instruments \| Interest Rate Caps \| Other assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative assets	0.0		0.7
Derivatives Designated as Hedging Instruments \| Interest Rate Caps \| Accrued expenses
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative liabilities	(2.4)		0.0
Derivatives Designated as Hedging Instruments \| Interest Rate Caps \| Other long-term liabilities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative liabilities		$ (1.7)	0.0
Derivatives Not Designated as Hedging Instruments \| Interest Rate Caps \| Prepaid expenses and other current assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative assets	$ 0.0		$ 5.8