Investments - Reconciliation of Net Unrealized Investment Gains (Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 1,567,285
Change in net unrealized investment gains (losses) on fixed maturity securities	(93,769)	$ 113,898
Ending balance	1,477,620	1,423,714
Net unrealized investment gains (losses) on securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	230,448	96,941
Ending balance	136,679	210,839
Net unrealized investment gains (losses) on securities \| Fixed maturity securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	264,410	111,712
Change in net unrealized investment gains (losses) on fixed maturity securities	(103,773)	140,012
Reclassification of net investment (gains) losses on securities to net income	(10,761)	(6,405)
Ending balance	$ 149,876	$ 245,319

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(31))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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