Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Summary of Significant Non-Cash Investing and Financing Activities (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022
Significant non-cash investing and financing activities
Other payable issued for agency acquisitions and purchased customer accounts	$ 4.9	$ 4.6
Estimated acquisition earn-out payables issued for agency acquisitions	$ 51.3	42.1
Assumed acquisition earn-out payables		34.8
Common stock issued for agency acquisition		14.7
Notes payable assumed for agency acquisition		$ 1.8

The amount of payables that an Entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482913/230-10-50-4

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482913/230-10-50-3

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482913/230-10-50-5

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