Equity (Schedule of Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Investment related gains (losses), net		$ 57,323	$ (9,312)	$ 87,036	$ (17,004)
Investment income		678,805	572,742	1,842,760	1,617,132
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest		347,090	322,661	823,731	707,874
Income Tax Expense (Benefit)		(84,325)	(21,462)	(188,761)	(102,071)
Net income		262,765	301,199	634,970	605,803
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		72,029	(25,858)	170,531	(79,505)
Income Tax Expense (Benefit)		(14,808)	5,355	(35,087)	16,978
Net income		57,221	(20,503)	135,444	(62,527)
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		50,537	(21,249)	70,513	(60,347)
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]	255	234	1,107	(108)
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]	(38)	50	(19)	270
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]	21,275	(4,893)	(98,930)	(19,320)
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		(835)	(1,620)	(3,728)	(3,986)
Income Tax Expense (Benefit)		175	340	783	837
Net income		(660)	(1,280)	(2,945)	(3,149)
Amounts Reclassified From AOCI [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net income		56,561	(21,783)	132,499	(65,676)
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]	267	246	804	739
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]	$ (1,102)	$ (1,866)	$ 4,532	$ (4,725)

[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.