Investments (Changes in Net Unrealized Gains on Investments) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investment Holdings [Line Items]
Fixed maturity securities held for investment carried at amortized cost	$ 2,947	$ (1,711)	$ (5,519)	$ 6,119
Investments carried at fair value, available for sale	(311,954)	128,524	(2,122,555)	1,008,004
Adjustment for effect on other balance sheet accounts:
Deferred policy acquisition costs and deferred sales inducements	172,566	(52,572)	1,132,853	(516,427)
Deferred income tax asset/liability	29,270	(26,583)	207,837	(172,052)
Total adjustment for effect on other balance sheet accounts	201,836	(79,155)	1,340,690	(688,479)
Change in net unrealized gains on investments carried at fair value	(110,118)	49,369	(781,865)	319,525
Fixed Maturity Securities
Investment Holdings [Line Items]
Investments carried at fair value, available for sale	(311,954)	128,981	(2,122,555)	1,008,483
Equity Securities
Investment Holdings [Line Items]
Investments carried at fair value, available for sale	$ 0	$ (457)	$ 0	$ (479)

No definition available.

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Adjustments for Assumed Changes in Amortization of Deferred Policy Acquisition Costs and Deferred Sales Inducements Due to Net Unrealized Gains and Losses on Available for Sale Fixed Maturity and Equity Securities.

+ References

No definition available.

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- Definition

Change in Net Unrealized Gain or Loss, Fixed Maturity Securities, Held for Investment

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No definition available.

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Represents the aggregate of the adjustments for the effect on other balance sheet accounts related to the pretax change in net unrealized holding gain (loss) on available-for-sale securities that has been included in accumulated other comprehensive income, a separate component of shareholders' equity, during the period.

+ References

No definition available.

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This item represents the pretax change in net unrealized holding gain (loss) on available-for-sale securities that has been included in accumulated other comprehensive income, a separate component of shareholders' equity, during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

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The change in unrealized holding gain (loss), net of tax, on available-for-sale securities included in a separate component of shareholders' equity during the period.

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This item represents the tax effects occurring during the period which are related to the net unrealized gain (loss) resulting from changes in the fair [carrying] value during the period of available-for-sale securities. Such tax affects would have been charged or credited directly to other comprehensive income or to related components of shareholders' equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=79507043&loc=d3e39076-109324

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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