IPO and Private Placement - Use of Proceeds from IPO (Details) - USD ($) $ in Millions		1 Months Ended		3 Months Ended	9 Months Ended
	Jul. 06, 2020	Feb. 07, 2019		Jun. 30, 2020	Sep. 30, 2020		Sep. 30, 2019		Feb. 08, 2019
Class of Stock [Line Items]
Gross proceeds	$ 2,381.0	$ 0.0			$ 0.0		$ 3,176.8
Underwriter fees	89.1
IPO related expenses	42.8	0.0	[1]		132.8	[1]	0.0	[1]
Redemption of Series A Preferred Stock	1,067.9	0.0			1,067.9		0.0
Make-whole payment on redemption of Series A Preferred Stock	205.2
Partial redemption of Notes and accrued interest		0.0			0.0		625.1
Call premium on partial redemption of Notes		$ 0.0			$ 2.5		$ 0.0
Cash to balance sheet	331.7
New Senior Unsecured Notes - 10.250%
Class of Stock [Line Items]
Partial redemption of Notes and accrued interest	312.0
Call premium on partial redemption of Notes	30.8
New Senior Unsecured Notes - 10.250% | Unsecured Debt
Class of Stock [Line Items]
Call premium on partial redemption of Notes				$ 30.8
Interest rate on debt instrument (as a percent)									10.25%
New Senior Secured Notes - 6.875%
Class of Stock [Line Items]
Partial redemption of Notes and accrued interest	282.2
Call premium on partial redemption of Notes	19.3
Star Parent, L.P. | Affiliated Entity
Class of Stock [Line Items]
IPO related expenses	30.0
THL Managers | Affiliated Entity
Class of Stock [Line Items]
IPO related expenses	2.5
Bilcar | Board of Directors Chairman
Class of Stock [Line Items]
IPO related expenses	2.5
CC Star Holdings, LP | Director
Class of Stock [Line Items]
IPO related expenses	$ 2.5

[1] $131.9 million was paid by proceeds raised from the offering (see Note 2) and $0.9 million was paid prior to the IPO and Private Placement.