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Revenue from Contracts with Customers - Summary of Expected Revenue Related to Performance Obligations (Detail) $ in Millions | Jun. 30, 2018 USD ($)
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Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | $ 471.8
2018 (Remaining Six Months) [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 294.2
2019 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 107.1
2020 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 28.1
2021 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 12.7
2022 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 7.2
Thereafter [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 22.5
Brokerage [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 294.7
Brokerage [Member] | 2018 (Remaining Six Months) [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 224.3
Brokerage [Member] | 2019 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 59.6
Brokerage [Member] | 2020 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 8.2
Brokerage [Member] | 2021 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 1.7
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 | 0.5
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 Six Months) [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 69.9
Risk Management [Member] | 2019 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 47.5
Risk Management [Member] | 2020 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 19.9
Risk Management [Member] | 2021 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 11.0
Risk Management [Member] | 2022 [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | 6.8
Risk Management [Member] | Thereafter [Member] |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
Expected revenue related to performance obligations | $ 22.0

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