Derivative Instruments (Financial Statement Classification and Impact of Derivatives Used in Qualifying and Non-qualifying Hedge Relationships) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net Realized Investments Gain Loss [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	$ (764,540)	$ (1,340,928)
Net investment income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	4,259	2,733
Other Income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	17,015	(1,556)
Accumulated Other Comprehensive Income (Loss)
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	102,856	1,623
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Net Realized Investments Gain Loss [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	1,855	(321)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Net investment income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	4,259	2,733
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Other Income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	16,943	(1,559)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Accumulated Other Comprehensive Income (Loss)
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	102,856	1,623
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Currency/Interest Rate | Net Realized Investments Gain Loss [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	1,855	(321)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Currency/Interest Rate | Net investment income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	4,259	2,733
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Currency/Interest Rate | Other Income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	16,943	(1,559)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Currency/Interest Rate | Accumulated Other Comprehensive Income (Loss)
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	102,856	1,623
Derivatives Not Qualifying as Hedge Accounting Instruments: | Net Realized Investments Gain Loss [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	(766,395)	(1,340,607)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Net investment income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Other Income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	72	3
Derivatives Not Qualifying as Hedge Accounting Instruments: | Accumulated Other Comprehensive Income (Loss)
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate | Net Realized Investments Gain Loss [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	7,049,901	992,444
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate | Net investment income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate | Other Income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate | Accumulated Other Comprehensive Income (Loss)
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency | Net Realized Investments Gain Loss [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	1,030	(186)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency | Net investment income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency | Other Income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency | Accumulated Other Comprehensive Income (Loss)
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency/Interest Rate | Net Realized Investments Gain Loss [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	41,849	1,831
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency/Interest Rate | Net investment income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency/Interest Rate | Other Income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	72	3
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency/Interest Rate | Accumulated Other Comprehensive Income (Loss)
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit Risk Contract | Net Realized Investments Gain Loss [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	(7,157)	(1)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit Risk Contract | Net investment income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit Risk Contract | Other Income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit Risk Contract | Accumulated Other Comprehensive Income (Loss)
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity | Net Realized Investments Gain Loss [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	5,015,288	(1,650,110)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity | Net investment income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity | Other Income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity | Accumulated Other Comprehensive Income (Loss)
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Embedded Derivative [Member] | Net Realized Investments Gain Loss [Member]
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	(12,867,306)	(684,585)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Embedded Derivative [Member] | Net investment income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Embedded Derivative [Member] | Other Income
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Embedded Derivative [Member] | Accumulated Other Comprehensive Income (Loss)
Derivative Instruments Gain Loss [Line Items]
Derivative Instruments Gain (Loss) Recognized In Income Net	$ 0	$ 0