Fair Value Measurements - Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets:
Fair Value	$ 408,046	$ 397,987
Equity securities at fair value	17,358	24,322
U.S. Governments
Assets:
Fair Value	19,311	17,059
States, territories, and possessions
Assets:
Fair Value	6,401	6,636
Political subdivisions
Assets:
Fair Value	1,588	2,152
Special revenue excluding mortgage/asset-backed securities
Assets:
Fair Value	44,430	41,227
Corporate and other
Assets:
Fair Value	255,100	245,360
Mortgage/asset-backed securities
Assets:
Fair Value	81,216	85,553
Fair Value, Measurements, Recurring
Assets:
Equity securities at fair value	17,358	24,322
Cash, cash equivalents, and restricted cash	41,634	33,786
Total assets	467,038	456,095
Fair Value, Measurements, Recurring \| U.S. Governments
Assets:
Fair Value	19,311	17,059
Fair Value, Measurements, Recurring \| States, territories, and possessions
Assets:
Fair Value	6,401	6,636
Fair Value, Measurements, Recurring \| Political subdivisions
Assets:
Fair Value	1,588	2,152
Fair Value, Measurements, Recurring \| Special revenue excluding mortgage/asset-backed securities
Assets:
Fair Value	44,430	41,227
Fair Value, Measurements, Recurring \| Corporate and other
Assets:
Fair Value	255,100	245,360
Fair Value, Measurements, Recurring \| Mortgage/asset-backed securities
Assets:
Fair Value	81,216	85,553
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1
Assets:
Equity securities at fair value	17,358	24,322
Cash, cash equivalents, and restricted cash	41,634	33,786
Total assets	58,992	58,108
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2
Assets:
Total assets	408,046	397,987
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| U.S. Governments
Assets:
Fair Value	19,311	17,059
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| States, territories, and possessions
Assets:
Fair Value	6,401	6,636
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Political subdivisions
Assets:
Fair Value	1,588	2,152
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Special revenue excluding mortgage/asset-backed securities
Assets:
Fair Value	44,430	41,227
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Corporate and other
Assets:
Fair Value	255,100	245,360
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Mortgage/asset-backed securities
Assets:
Fair Value	$ 81,216	$ 85,553

Fair value portion of cash, cash equivalents and restricted cash.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

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-Publisher FASB
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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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