Fair Value of Financial Instruments - Rollforward of Instruments Measured on Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Financial Assets
Beginning balance	$ 295,178	$ 248,489
Transfers into Level 3	105,059	25,008
Transfers out of Level 3	(12,969)	0
Total gains or losses
Net investment gains (losses) included in net income related to financial assets	(24)	0
Net unrealized investment gains (losses) included in OCI	(32,869)	2,741
Purchases	8,765	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Paydowns, maturities and distributions	(5,945)	(10,205)
Ending balance	357,195	266,033
Financial Liabilities
Beginning balance	93,733	78,700
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Total gains or losses
Net realized (gains) losses included in net income related to financial liabilities	(5,042)	4,334
Net unrealized investment gains (losses) included in OCI	0	0
Purchases	0	0
Issuances	1,354	3,018
Sales	0	0
Settlements	0	0
Paydowns, maturities and distributions	(2,539)	(1,423)
Ending balance	87,506	84,629
Total Fixed Maturity Securities
Financial Assets
Beginning balance	295,071	248,484
Transfers into Level 3	105,059	25,008
Transfers out of Level 3	(12,969)	0
Total gains or losses
Net investment gains (losses) included in net income related to financial assets	0	0
Net unrealized investment gains (losses) included in OCI	(32,869)	2,741
Purchases	8,765	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Paydowns, maturities and distributions	(5,945)	(10,205)
Ending balance	357,112	266,028
Municipal bonds
Financial Assets
Beginning balance	44,291	47,531
Transfers into Level 3	63,751	0
Transfers out of Level 3	0	0
Total gains or losses
Net investment gains (losses) included in net income related to financial assets	0	0
Net unrealized investment gains (losses) included in OCI	(3,026)	344
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Paydowns, maturities and distributions	(124)	(119)
Ending balance	104,892	47,756
Corporate bonds
Financial Assets
Beginning balance	103,952	80,742
Transfers into Level 3	18,833	3,074
Transfers out of Level 3	(10,022)	0
Total gains or losses
Net investment gains (losses) included in net income related to financial assets	0	0
Net unrealized investment gains (losses) included in OCI	(5,481)	2,549
Purchases	6,875	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Paydowns, maturities and distributions	(2,464)	(3,883)
Ending balance	111,693	82,482
Mortgage-Backed Securities
Financial Assets
Beginning balance	146,828	120,211
Transfers into Level 3	22,475	21,934
Transfers out of Level 3	(2,947)	0
Total gains or losses
Net investment gains (losses) included in net income related to financial assets	0	0
Net unrealized investment gains (losses) included in OCI	(24,362)	(152)
Purchases	1,890	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Paydowns, maturities and distributions	(3,357)	(6,203)
Ending balance	140,527	135,790
Equity securities
Financial Assets
Beginning balance	107	5
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Total gains or losses
Net investment gains (losses) included in net income related to financial assets	(24)	0
Net unrealized investment gains (losses) included in OCI	0	0
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Paydowns, maturities and distributions	0	0
Ending balance	$ 83	$ 5

Fair value measurement with unobservable inputs reconciliation recurring basis asset paydowns and maturities.

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Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liability Paydowns And Maturities

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Gain Or Loss Net [Abstract]

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Amount of transfers of financial instrument classified as a liability into level 3 of the fair value hierarchy.

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Amount of transfers of financial instrument classified as a liability out of level 3 of the fair value hierarchy.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of gain (loss) recognized in other comprehensive income (OCI) from liability measured at fair value on recurring basis using unobservable input (level 3).

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Amount of issuances of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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