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Contracts with Customers - Summary of Expected Revenue Related to Performance Obligations 1 (Detail) $ in Millions	Sep. 30, 2020 USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 531.4
Brokerage [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	345.4
Risk Management [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 186.0

X

- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

+ Details

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X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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