Temporary Equity, Equity and Dividends (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions						1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 20, 2023	Mar. 07, 2023	Feb. 01, 2023	Jan. 22, 2023	Jan. 03, 2023	Nov. 09, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Dividends Payable [Line Items]
Issuance of common stock									$ 15.0
Vesting period									3 years
Dividend paid									$ 21.9	$ 0.0
Loss from intra-entity foreign currency transactions							$ 4.9	$ 10.2	$ 4.3	19.6
Special Dividend
Dividends Payable [Line Items]
Dividends declared (usd per share)		$ 1.08							$ 1.08
Preferential Dividends
Dividends Payable [Line Items]
Preferred Stock, dividends							6.7		$ 17.6
Dividend paid									16.5
Dividends accrued and unpaid							1.1		1.1
Participating Dividends
Dividends Payable [Line Items]
Preferred Stock, dividends							1.8		5.4
Securities Purchase Agreement
Dividends Payable [Line Items]
Initial conversion price (usd per share)			$ 73.00
Starboard Value LP and certain of its affiliates | Securities Purchase Agreement
Dividends Payable [Line Items]
Issuance of common stock			$ 15.0
Shares issued for business combination
Dividends Payable [Line Items]
Share capital from additional paid-in capital							0.3	0.3	0.3	0.3
Unrecognized share based continuing employment costs							$ 0.9	$ 4.7	$ 0.9	$ 4.7
Unrecognized share based continuing employment costs, weighted average period for recognition									8 months 12 days
VeriTread
Dividends Payable [Line Items]
Non-controlling interest, percentage					4.00%
Senior A Senior Preferred Shares
Dividends Payable [Line Items]
Temporary equity, authorized shares (in shares)							485,000,000		485,000,000
Issuance of redeemable convertible preferred stock									$ 482.0
Senior A Senior Preferred Shares | Starboard Value LP and certain of its affiliates | Securities Purchase Agreement
Dividends Payable [Line Items]
Issuance of redeemable convertible preferred stock			$ 485.0
Initial preferred dividend, percentage			5.50%
Participating dividends (usd per share)			$ 0.27
Increase in preferred dividend rate in fourth anniversary, percentage			7.50%
Spread on variable rate, percentage			6.00%
Increase in preferred dividend rate in ninth anniversary, percentage			10.50%
Notice term for redemption of preferred shares			45 days
Redemption price, percentage			100.00%
Subsequent Event
Dividends Payable [Line Items]
Dividends declared (usd per share)						$ 0.27
IAA
Dividends Payable [Line Items]
Cash consideration	$ 1,714.2			$ 1,700.0
VeriTread
Dividends Payable [Line Items]
Prior holdings of issued and outstanding shares, percent					11.00%
Voting equity interests owned including previous interest, percentage					75.00%
Cash consideration					$ 28.1
Remaining units ownership interest, percentage					21.00%