Acquisitions and Divestitures (Narrative) (Details) $ / shares in Units, shares in Millions, $ in Millions								3 Months Ended	12 Months Ended
	Nov. 28, 2025 USD ($)	Nov. 03, 2025 USD ($)	Jul. 14, 2025 USD ($)	Oct. 31, 2024 USD ($)	Mar. 20, 2023 USD ($)	Jan. 22, 2023 USD ($) $ / shares shares	Jan. 03, 2023 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Business Combination [Line Items]
Acquisitions, net of cash acquired			$ 163.6						$ 192.8	$ 8.6	$ 2,778.6
Goodwill								$ 4,668.0	$ 4,668.0	4,511.8	$ 4,537.0
Discontinued Operations, Disposed of by Sale | DDI
Business Combination [Line Items]
Consideration received from sale		$ 37.8
Gain on disposition of business		$ 5.9
JM Wood Auction Co Inc
Business Combination [Line Items]
Voting equity interests owned			100.00%
Contingent consideration liability			$ 43.1
Business combination, consideration transferred, measurement period adjustment								25.2
Goodwill, measurement period adjustment								$ 25.2
Acquiree's revenue, prior period										$ 92.6
Total purchase price			213.6
Goodwill			$ 145.8
Weighted-average amortization period			6 years 9 months 18 days
JM Wood Auction Co Inc | Accounts Payable and Accrued Liabilities
Business Combination [Line Items]
Contingent consideration liability			$ 13.8
JM Wood Auction Co Inc | Other Noncurrent Liabilities
Business Combination [Line Items]
Contingent consideration liability			$ 29.3
IAA
Business Combination [Line Items]
Total purchase price					$ 6,646.1
Cash consideration per share (usd per share) | $ / shares						$ 12.80
Shares issued per share						0.5252
Purchase consideration					1,714.2	$ 1,700.0
Common stock consideration (in shares) | shares						70.3
Assumption of net debt						$ 1,200.0
Goodwill					$ 3,546.6
Weighted-average amortization period					13 years 4 months 24 days
IAA | 2021 Notes
Business Combination [Line Items]
Assumption of net debt						$ 500.0
Redemption price percentage						102.75%
Smith Broughton Pty Ltd
Business Combination [Line Items]
Total purchase price	$ 31.2
Goodwill	$ 8.3
Smith Broughton Pty Ltd | Minimum
Business Combination [Line Items]
Weighted-average amortization period	5 years
Smith Broughton Pty Ltd | Maximum
Business Combination [Line Items]
Weighted-average amortization period	7 years
Boom and Bucket Inc
Business Combination [Line Items]
Total purchase price				$ 10.0
Weighted-average amortization period				3 years
VeriTread
Business Combination [Line Items]
Total purchase price							$ 32.4
Purchase consideration							28.1
Goodwill							$ 25.2
Aggregate holdings of issued and outstanding shares							75.00%
Prior holdings of issued and outstanding shares							11.00%
Equity interest, fair value							$ 4.3