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Commitments, Contingencies and Off-Balance Sheet Arrangements - Litigation, Regulatory and Taxation Matters- Additional Information (Detail) $ in Millions | 9 Months Ended | 24 Months Ended
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Sep. 30, 2018 Companies | Dec. 31, 2017 USD ($)
Minimum [Member] |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |
Number of micro-captive insurance companies organized or managed | Companies | 100 |
Micro-captive operations, net earnings and EBITDAC, description | In the period from 2015 to 2017, our micro-captive operations contributed less than $3.5 million of net earnings and less than $5.0 million in EBITDAC to our consolidated results in any one year. |
Maximum [Member] |  |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |
Micro-captive operations, net earnings |  | $ 3.5
Micro-captive operations, EBITDAC |  | $ 5.0

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- Definition Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] + References No definition available. + Details
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