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Investments (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
Investments (Narrative) (Details) $ in Thousands	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Investment Narrative [Line Items]
Document Period End Date			Sep. 30, 2019
Funds Held Under Reinsurance Agreements Asset Specific Client	$ 3,600,000		$ 3,600,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	3,700		3,700
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash	27,500		27,500		$ 28,600
Net Amount Assets Liabilities From Repurchase Reverse Repurchase Agreements	500		500		$ 400
Proceeds From Sale Of Available For Sale Securities Sold At Loss	1,313,700	$ 1,345,300	3,026,500	$ 3,783,300
Available-for-sale Securities, Realized Losses, Excluding Other than Temporary Impairments	$ 12,996	37,880	$ 38,589	94,194
Policy Loans Percent Of Total Investments	2.00%		2.00%		2.50%
Mortgage Loan Percent Of Cash And Invested Assets	8.80%		8.80%		9.10%
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	856		856		3,109
Securities As Percentage Of Consolidated Stockholder Equity	10.00%		10.00%
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	100.00%		100.00%		100.00%
Funds Withheld At Interest Percent Of Total Investments	8.70%		8.70%		10.60%
Funds withheld at interest	$ 5,614,363		$ 5,614,363		$ 5,761,471
Other Invested Assets Percent Of Cash And Invested Assets	3.40%		3.40%		3.50%
ProceedsFromSaleOfAvailableForSaleEquitySecuritiesSoldAtLoss				31,500
Available-for-sale Equity Securities, Gross Unrealized Loss	$ 0	$ 174	$ 1	$ 1,124
CALIFORNIA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	17.00%		17.00%
TEXAS
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	12.90%		12.90%
WASHINGTON
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	7.40%		7.40%
CANADA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	2.90%		2.90%
UNITED KINGDOM
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	0.50%		0.50%