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

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

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss.

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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Investments - Narrative (Details)		3 Months Ended				6 Months Ended
Investments - Narrative (Details)	Jun. 30, 2019 USD ($) issuer	Jun. 30, 2019 USD ($) issuer	Mar. 31, 2019 USD ($) security	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Jun. 30, 2019 USD ($) issuer loan	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Gain (Loss) on Securities [Line Items]
Number of issuers \| issuer	77	77				77
Total fair value	$ 281,721,000	$ 281,721,000				$ 281,721,000
Gross unrealized losses	3,117,000	3,117,000				3,117,000
Fixed maturity securities, available-for-sale	1,332,042,000	1,332,042,000				$ 1,332,042,000		$ 1,184,202,000
Number of impaired loans \| loan						2
Carrying value of impaired loans	3,400,000	3,400,000				$ 3,400,000
Unpaid principal on impaired loans	3,600,000	3,600,000				3,600,000
Allowance for credit losses on impaired loans	231,000	231,000		$ 1,200,000		231,000	$ 1,200,000		$ 3,200,000
Average recorded investment in impaired bank loans						1,700,000	3,700,000
Investment income during period loans were impaired						0	65,000
Net realized gain (loss) on changes in fair value of impaired bank loans		231,000		896,000		1,800,000	893,000
Net realized and unrealized gains (losses) on investments		1,063,000		$ (64,000)		2,688,000	$ (874,000)
Carrying value of collateralized loan obligation held	3,400,000	3,400,000				3,400,000
Fixed maturity securities
Gain (Loss) on Securities [Line Items]
Total fair value								852,854,000
Gross unrealized losses								21,267,000
Fixed maturity securities, available-for-sale	$ 1,332,042,000	$ 1,332,042,000				$ 1,332,042,000		$ 1,184,202,000
Number of impaired fixed maturities \| security			3
Impairment losses			$ 271,000
Puerto Rico loan
Gain (Loss) on Securities [Line Items]
Carrying value of impaired loans									0
Unpaid principal on impaired loans									$ 807,000
Net realized and unrealized gains (losses) on investments					$ 807,000
BBB- or better \| Fixed maturity securities
Gain (Loss) on Securities [Line Items]
Percentage of available for sale securities	99.60%	99.60%				99.60%
Below BBB-
Gain (Loss) on Securities [Line Items]
Fixed maturity securities, available-for-sale	$ 5,300,000	$ 5,300,000				$ 5,300,000
Aggregate net unrealized gain (loss)	$ 48,000