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Revenue from Contracts with Customers - Summary of Expected Revenue Related to Performance Obligations (Detail) $ in Millions | Mar. 31, 2018 USD ($)
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Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | $ 465.2
2018 (Remaining Nine Months) [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 329.3
2019 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 80.8
2020 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 30.3
2021 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 11.7
2022 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 5.1
Thereafter [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 8.0
Brokerage [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 288.1
Brokerage [Member] | 2018 (Remaining Nine Months) [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 244.0
Brokerage [Member] | 2019 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 31.7
Brokerage [Member] | 2020 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 9.0
Brokerage [Member] | 2021 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 2.8
Brokerage [Member] | 2022 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 0.4
Brokerage [Member] | Thereafter [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 0.2
Risk Management [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 177.1
Risk Management [Member] | 2018 (Remaining Nine Months) [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 85.3
Risk Management [Member] | 2019 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 49.1
Risk Management [Member] | 2020 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 21.3
Risk Management [Member] | 2021 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 8.9
Risk Management [Member] | 2022 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 4.7
Risk Management [Member] | Thereafter [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | $ 7.8

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- 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=84173487&loc=SL51747714-108306 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 13 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130556-203045 + Details
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