Accumulated other comprehensive loss related to portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized as available-for-sale that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.

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Investments in Fixed Maturity Securities (Narrative) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items]
Held-to-maturity Securities, Restricted	$ 995,000,000
Insurance-related Assessments [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items]
Held-to-maturity Securities, Restricted	308,000,000
Reinsurance
Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items]
Held-to-maturity Securities, Restricted	46,000,000
Letters of Credit Outstanding, Amount	4,000,000
523991 Trust, Fiduciary, and Custody Activities [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items]
Held-to-maturity Securities, Restricted	1,353,000,000
Residential mortgage-backed
Schedule of Available-for-sale and Held-to-maturity Securities [Table] [Line Items]
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ 76,467	$ (818,691)