Investments - Summary of Available-for-Sale Gross Unrealized Gains or Losses by Investment Type (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, change in gross unrealized gains (losses)	$ 50,300	$ (22,643)	$ 11,927
Fixed maturity securities:
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, change in gross unrealized gains (losses)	50,300	(22,643)	6,571
Equity securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, change in gross unrealized gains (losses)	$ 0	$ 0	$ 5,356

Amount before tax, after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118930883&loc=d3e637-108580

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration