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Commitments, Contingencies and Off-Balance Sheet Arrangements - Litigation, Regulatory and Taxation Matters- Additional Information (Detail)	3 Months Ended
	Mar. 31, 2018 Companies
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Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Number of micro-captive insurance companies organized or managed	100

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Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]

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Micro captive Insurance Companies Managed

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