Investments (Narrative) (Details) $ in Thousands	Sep. 30, 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	220	1,005
Available-for-sale securities, estimated fair value	$ 947,715	$ 4,594,664
Available-for-sale securities, gross unrealized holding losses	$ (23,819)	$ (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	162	541
Available-for-sale securities, estimated fair value, 12 months or longer	$ 495,569	$ 1,983,912
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(11,065)	(77,504)
Fixed Maturities [Member]
Schedule of Investments [Line Items]
Available-for-sale securities, estimated fair value	832,576	4,397,021
Available-for-sale securities, gross unrealized holding losses	(22,719)	(131,215)
Available-for-sale securities, estimated fair value, 12 months or longer	495,569	1,983,912
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	$ (11,065)	$ (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, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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