Equity (Schedule of Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other investment related gains (losses), net										$ (107,370)	$ 193,959	$ 76,891
Investment income, net of related expenses										1,734,495	1,713,691	1,699,865
Deferred Policy Acquisition Cost, Amortization Expense, Unrealized Investment Gains (Losses)										(17,510)	4,480	(16,181)
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax										(337)	(485)	(525)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax										(4,618)	43,025	(21,624)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest		$ 206,743	$ 140,137	$ 213,790	$ 184,125	$ 276,743	$ 231,815	$ 300,535	$ 199,440	744,795	1,008,533	635,254
Income Tax Expense (Benefit)										(242,629)	(324,486)	(216,417)
Net Income (Loss) Attributable to Parent		$ 163,127	$ 83,534	$ 130,391	$ 125,114	$ 191,091	$ 157,996	$ 198,296	$ 136,664	502,166	684,047	$ 418,837
Amortization Of Unrealized Pension And Postretirement Benefits [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax	[1]									(309)	333
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax	[1]									(5,894)	(2,815)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest										(6,203)	(3,148)
Income Tax Expense (Benefit)										2,171	1,082
Net Income (Loss) Attributable to Parent										(4,032)	(2,066)
Unrealized Appreciation Depreciation Of Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other investment related gains (losses), net										(55,767)	26,405
Investment income, net of related expenses	[2]									569	1,212
Deferred Policy Acquisition Cost, Amortization Expense, Unrealized Investment Gains (Losses)	[3]									(17,510)	4,480
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest										(72,795)	32,097
Income Tax Expense (Benefit)										28,109	(7,319)
Net Income (Loss) Attributable to Parent										(44,686)	24,778
Amounts Reclassified From AOCI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income (Loss) Attributable to Parent										(48,718)	22,712
Unrealized Gains Losses On Available For Sale Securities [Member] | Unrealized Appreciation Depreciation Of Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	[2]									$ (87)	$ 0

[1] See Note 10 for information on employee benefit plans.

[2] See Note 5 for information on cash flow hedges.

[3] See Note 8 for information on deferred policy acquisition costs.