Derivative Instruments (Changes in Estimated Fair Value Related to Embedded Derivatives) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	$ 60,523	$ (120,886)
Gain Loss On Investments Related To Change In Fair Value Of Derivatives Excluding Embedded Derivatives	(22,849)	54,102
Total benefits and expenses	2,800,896	2,404,988
Net income	145,512	76,472
Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	68,702	(92,250)
Net income	25,844	(26,777)
Embedded Derivatives In Equity Indexed Annuities [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total benefits and expenses	(16,402)	1,394
Net income	(21,396)	11,234
Embedded Derivatives In Variable Annuity Contracts [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	22,363	(62,940)
Net income	$ 28,836	$ (25,843)

Changes in estimated fair value related to embedded derivatives Abstract.

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This item represents the amount recognized in investment related gains (losses) related to the change in the fair value of derivatives, excluding embedded derivatives.

+ References

No definition available.

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- Definition

The total amount of expense recognized during the period for future policy benefits, claims and claims adjustment costs, and for selling, general and administrative costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
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This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments.

+ References

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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