Insurance Operations - Reinsurance Transactions (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)
Reinsurance
Reinsurers with largest obligations, number \| item	3
Allowance for uncollectible reinsurance	$ 0.5
Aggregate reinsurers’ ceding participation (as a percent)	26.00%
Whole Account Quota Share Reinsurance Agreement
Reinsurance
Reinsurance receivable unpaid	$ 33.1	$ 43.7
Minimum \| Whole Account Quota Share Reinsurance Agreement
Reinsurance
Provisional ceding commission (as a percent)	30.00%
Maximum \| Whole Account Quota Share Reinsurance Agreement
Reinsurance
Provisional ceding commission (as a percent)	30.50%
Reinsurance receivables
Reinsurance
Allowance for uncollectible reinsurance	$ 10.9	$ 10.0
Swiss Reinsurance America Corporation \| Reinsurance receivables paid, reinsurance receivables unpaid and prepaid reinsurance premiums
Reinsurance
Reinsurers with largest obligations (as a percent)	31.30%
Munich Reinsurance Company \| Reinsurance receivables paid, reinsurance receivables unpaid and prepaid reinsurance premiums
Reinsurance
Reinsurers with largest obligations (as a percent)	14.20%
Harco National Insurance Company \| Reinsurance receivables paid, reinsurance receivables unpaid and prepaid reinsurance premiums
Reinsurance
Reinsurers with largest obligations (as a percent)	9.00%

The percentage of provisional ceding commission received as a reduction in the amount of ceded premium.

No definition available.

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- Definition

The number of reinsurers with largest obligations to the Company.

+ References

No definition available.

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- Definition

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.

+ Details

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
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-Paragraph 18
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- Definition

Ratio of insurance contracts that are subject to reinsurance participation to all contracts in force.

+ References

No definition available.

+ Details

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- Definition

Amount of reinsurance recoverable past due.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919253-210447

+ Details

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- Definition

Amount of allowance for credit loss on reinsurance recoverable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
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-URI http://asc.fasb.org/extlink&oid=118955202&loc=SL82895884-210446

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