Schedule I - Summary of Investments-Other Than Investments in Related Parties (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investments-Other Than Investments in Related Parties
Amortized Cost	$ 4,485,953
Fair Value	4,654,277	$ 3,429,620
Amount at which shown in the Balance Sheet	4,654,277
Fixed maturities
Investments-Other Than Investments in Related Parties
Amortized Cost	3,677,815
Fair Value	3,838,513
Amount at which shown in the Balance Sheet	3,838,513
Fixed maturities \| United States Government and government agencies and authorities
Investments-Other Than Investments in Related Parties
Amortized Cost	1,212,622
Fair Value	1,254,075
Amount at which shown in the Balance Sheet	1,254,075
Fixed maturities \| States, municipalities and political subdivisions
Investments-Other Than Investments in Related Parties
Amortized Cost	513,870
Fair Value	551,517
Amount at which shown in the Balance Sheet	551,517
Fixed maturities \| Residential and commercial mortgage securities
Investments-Other Than Investments in Related Parties
Amortized Cost	391,921
Fair Value	409,282
Amount at which shown in the Balance Sheet	409,282
Fixed maturities \| Asset-backed securities
Investments-Other Than Investments in Related Parties
Amortized Cost	452,527
Fair Value	454,717
Amount at which shown in the Balance Sheet	454,717
Fixed maturities \| Foreign government and agency securities
Investments-Other Than Investments in Related Parties
Amortized Cost	56,045
Fair Value	61,607
Amount at which shown in the Balance Sheet	61,607
Fixed maturities \| All other corporate bonds
Investments-Other Than Investments in Related Parties
Amortized Cost	1,050,830
Fair Value	1,107,315
Amount at which shown in the Balance Sheet	1,107,315
Short-term investments
Investments-Other Than Investments in Related Parties
Amortized Cost	726,875
Fair Value	726,860
Amount at which shown in the Balance Sheet	726,860
Other invested assets
Investments-Other Than Investments in Related Parties
Amortized Cost	81,263
Fair Value	88,904
Amount at which shown in the Balance Sheet	$ 88,904

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Sum of the carrying amounts as of the balance sheet date of all investments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 7
-Subparagraph (SX 210.12-15(Column D))
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Cost of investment held by insurance company, excluding investment in related party.

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-SubTopic 320
-Section S99
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