Equity (Schedule of Reclassifications out of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other investment related gains (losses), net										$ 132,926	$ (107,370)	$ 193,959
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities										(74)	0	0
Investment income, net of related expenses										1,911,886	1,734,495	1,713,691
Deferred Policy Acquisition Cost, Amortization Expense, Unrealized Investment Gains (Losses)										3,541	(17,510)	4,480
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax										(444)	(337)	(485)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax										(4,427)	(4,618)	43,025
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest		$ 295,543	$ 287,600	$ 353,223	$ 107,580	$ 206,743	$ 140,137	$ 213,790	$ 184,125	1,043,946	744,795	1,008,533
Income Tax Expense (Benefit)										(342,503)	(242,629)	(324,486)
Net Income (Loss) Attributable to Parent		$ 190,149	$ 198,719	$ 236,103	$ 76,472	$ 163,127	$ 83,534	$ 130,391	$ 125,114	701,443	502,166	$ 684,047
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]									328	309
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax	[1]									(6,150)	(5,894)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest										(5,822)	(6,203)
Income Tax Expense (Benefit)										2,038	2,171
Net Income (Loss) Attributable to Parent										(3,784)	(4,032)
Unrealized Appreciation Depreciation Of Investments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other investment related gains (losses), net										65,798	(55,767)
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Loss, before Tax, Including Portion Attributable to Noncontrolling Interest, Available-for-sale Securities										74	0
Deferred Policy Acquisition Cost, Amortization Expense, Unrealized Investment Gains (Losses)	[2]									3,541	(17,510)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest										69,622	(72,795)
Income Tax Expense (Benefit)										(17,672)	28,109
Net Income (Loss) Attributable to Parent										51,950	(44,686)
Amounts Reclassified From AOCI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income (Loss) Attributable to Parent										48,166	(48,718)
Currency Swap [Member] | 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	[3]									510	569
Forward Contracts [Member] | 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	[3]									$ (301)	$ (87)

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

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

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