Number of customers where transactions amount to 10 percent or more of the entity's revenues.

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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.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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- Definition

The carrying value as of the balance sheet date of the estimated valuation allowance to reduce gross premiums receivable to net realizable value.

+ References

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Amount of writeoff of premium receivable, charged against allowance for credit loss.

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COMMITMENTS AND CONTINGENCIES - Reinsurance and premiums (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) broker	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Concentration Risk [Line Items]
Premium Receivable, Allowance for Credit Loss	$ 8,836,000	$ 7,000,000
Premiums receivable, bad debt expense charges	$ 0	$ 0	$ 0
Reinsurance Recoverable On Unpaid And Paid Losses \| Reinsurer Concentration \| Reinsurer 1
Concentration Risk [Line Items]
Concentration risk, percentage of total	13.00%	12.00%
Reinsurance Recoverable On Unpaid And Paid Losses \| Reinsurer Concentration \| Reinsurer 2
Concentration Risk [Line Items]
Concentration risk, percentage of total	10.00%	10.00%
Reinsurance Recoverable On Unpaid And Paid Losses \| Reinsurer Concentration \| Reinsurer 3
Concentration Risk [Line Items]
Concentration risk, percentage of total	7.00%	9.00%
Reinsurance Recoverable On Unpaid And Paid Losses \| Reinsurer Concentration \| Top Ten Reinsurers \| AM Best, A- Rating
Concentration Risk [Line Items]
Concentration risk, percentage of total	87.60%	89.10%
Gross Premiums Written \| Customer Concentration
Concentration Risk [Line Items]
Concentration risk, percentage of total	47.00%	47.00%	43.00%
Concentration risk, number of brokers exceeding threshold \| broker	3
Gross Premiums Written \| Customer Concentration \| Marsh & McLennan Companies Inc.
Concentration Risk [Line Items]
Concentration risk, percentage of total	19.00%	18.00%	17.00%
Gross Premiums Written \| Customer Concentration \| Aon plc
Concentration Risk [Line Items]
Concentration risk, percentage of total	17.00%	19.00%	17.00%
Gross Premiums Written \| Customer Concentration \| Willis Towers Watson PLC
Concentration Risk [Line Items]
Concentration risk, percentage of total	11.00%	10.00%	9.00%