Investments (Narrative) (Details) $ in Thousands	Mar. 31, 2019 USD ($) securities	Dec. 31, 2018 USD ($) securities
Schedule of Investments [Line Items]
Available-for-sale fixed maturity securities in unrealized loss position, number of positions \| securities	618	1,005
Available-for-sale securities, estimated fair value	$ 2,316,186	$ 4,594,664
Available-for-sale securities, gross unrealized holding losses	$ (53,257)	$ (133,989)
Number of available-for-sale fixed maturity securities positions in a continuous unrealized loss position for one year or longer at period end \| securities	560	541
Available-for-sale securities, estimated fair value, 12 months or longer	$ 2,032,512	$ 1,983,912
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(47,516)	(77,504)
Fixed Maturities [Member]
Schedule of Investments [Line Items]
Available-for-sale securities, estimated fair value	2,241,936	4,397,021
Available-for-sale securities, gross unrealized holding losses	(52,151)	(131,215)
Available-for-sale securities, estimated fair value, 12 months or longer	2,032,512	1,983,912
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	$ (47,516)	$ (77,504)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
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-Publisher FASB
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-Topic 320
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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.

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