Investments (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Investment Narrative [Line Items]
Document Period End Date			Jun. 30, 2019
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	28,600		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	466,100	$ 1,174,400	1,712,700	$ 2,438,000
Available-for-sale Securities, Realized Losses, Excluding Other than Temporary Impairments	$ 6,870	35,934	$ 25,593	56,314
Policy Loans Percent Of Total Investments	2.20%		2.20%		2.50%
Mortgage Loan Percent Of Cash And Invested Assets	8.90%		8.90%		9.10%
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	921		921		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	9.30%		9.30%		10.60%
Funds withheld at interest	$ 5,696,217		$ 5,696,217		$ 5,761,471
Funds Held Under Reinsurance Agreements Asset Specific Client	$ 3,600,000		$ 3,600,000
Other Invested Assets Percent Of Cash And Invested Assets	3.50%		3.50%
ProceedsFromSaleOfAvailableForSaleEquitySecuritiesSoldAtLoss				28,400
Available-for-sale Equity Securities, Gross Unrealized Loss	$ 0	$ 0	$ 1	$ 950
CALIFORNIA
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	16.80%		16.80%
TEXAS
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	13.40%		13.40%
WASHINGTON
Investment Narrative [Line Items]
Mortgage Loans On Real Estate Commercial And Consumer Net Percentage Of Total	7.10%		7.10%
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%