Equity (Schedule of Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Investment related gains (losses), net		$ 12,472	$ (7,222)	$ 29,713	$ (7,692)
Investment income		584,078	528,061	1,163,955	1,044,390
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest		260,077	247,288	476,641	385,213
Income Tax Expense (Benefit)		(57,379)	(42,914)	(104,436)	(80,609)
Net income		202,698	204,374	372,205	304,604
Unrealized Appreciation Depreciation Of Investments [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest		83,808	(32,372)	98,502	(53,646)
Income Tax Expense (Benefit)		(17,273)	6,945	(20,279)	11,623
Net income		66,535	(25,427)	78,223	(42,023)
Unrealized Appreciation Depreciation Of Investments [Member] | Unrealized Gains Losses On Available For Sale Securities [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Investment related gains (losses), net		20,249	(24,642)	19,976	(39,098)
Unrealized Appreciation Depreciation Of Investments [Member] | Interest Rate Swap [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	[1]	383	29	852	(342)
Unrealized Appreciation Depreciation Of Investments [Member] | Currency Swap [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	[1]	(6)	76	19	221
Unrealized Appreciation Depreciation Of Investments [Member] | DAC Attributed To Unrealized Gains Losses [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Deferred policy acquisition costs attributed to unrealized gains and losses	[2]	63,182	(7,835)	(77,655)	(14,427)
Amortization Of Unrealized Pension And Postretirement Benefits [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest		(1,607)	(1,020)	(2,893)	(2,366)
Income Tax Expense (Benefit)		338	214	608	497
Net income		(1,269)	(806)	(2,285)	(1,869)
Amounts Reclassified From AOCI [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net income		65,266	(26,233)	75,938	(43,892)
Prior Service Cost [Member] | Amortization Of Unrealized Pension And Postretirement Benefits [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Prior service cost	[3]	268	247	537	493
Actuarial Gains Losses [Member] | Amortization Of Unrealized Pension And Postretirement Benefits [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Actuarial gains/(losses)	[3]	$ (1,875)	$ (1,267)	$ 3,430	$ (2,859)

[1] See Note 5 - “Derivative Instruments” for additional information on cash flow hedges.

[2] This AOCI component is included in the computation of the deferred policy acquisition cost. See Note 8 – “Deferred Policy Acquisition Costs” of the 2018 Annual Report for additional details.

[3] This AOCI component is included in the computation of the net periodic pension cost. See Note 10 – “Employee Benefit Plans” for additional details.