Fair Values of Financial Instruments (Assets and Liabilities Measured on a Recurring Basis by Fair Value Hierarchy) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets
Derivative instruments	$ 1,509,892	$ 1,310,954
Liabilities
Equity method investments, fair value	180,100	179,700
COLI, fair value	374,900	373,600
Fair Value, Measurements, Recurring
Assets
Derivative instruments	1,509,892	1,310,954
Cash and cash equivalents	11,087,125	9,095,522
Assets	58,639,910	57,945,369
Liabilities
Fixed index annuities - embedded derivatives	7,680,951	7,938,281
Fair Value, Measurements, Recurring \| United States Government Full Faith and Credit
Assets
Investments	38,727	39,771
Fair Value, Measurements, Recurring \| United States Government Sponsored Agencies
Assets
Investments	1,027,441	1,039,551
Fair Value, Measurements, Recurring \| United States Municipalities, States and Territories
Assets
Investments	3,655,844	3,776,131
Fair Value, Measurements, Recurring \| Foreign Government Obligations
Assets
Investments	193,944	202,706
Fair Value, Measurements, Recurring \| Corporate Securities
Assets
Investments	29,890,265	31,156,827
Fair Value, Measurements, Recurring \| Residential Mortgage Backed Securities
Assets
Investments	1,346,473	1,512,831
Fair Value, Measurements, Recurring \| Commercial Mortgage Backed Securities
Assets
Investments	4,177,242	4,261,227
Fair Value, Measurements, Recurring \| Other Asset Backed Securities
Assets
Investments	5,360,405	5,549,849
Fair Value, Measurements, Recurring \| Equity Securities
Assets
Investments	352,552
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1)
Assets
Derivative instruments	0	0
Cash and cash equivalents	11,087,125	9,095,522
Assets	11,470,364	9,129,470
Liabilities
Fixed index annuities - embedded derivatives	0	0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| United States Government Full Faith and Credit
Assets
Investments	33,228	33,940
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| United States Government Sponsored Agencies
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| United States Municipalities, States and Territories
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| Foreign Government Obligations
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| Corporate Securities
Assets
Investments	11	8
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| Residential Mortgage Backed Securities
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| Commercial Mortgage Backed Securities
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| Other Asset Backed Securities
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| Equity Securities
Assets
Investments	350,000
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Assets
Derivative instruments	1,509,892	1,310,954
Cash and cash equivalents	0	0
Assets	47,169,546	48,815,899
Liabilities
Fixed index annuities - embedded derivatives	0	0
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| United States Government Full Faith and Credit
Assets
Investments	5,499	5,831
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| United States Government Sponsored Agencies
Assets
Investments	1,027,441	1,039,551
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| United States Municipalities, States and Territories
Assets
Investments	3,655,844	3,776,131
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Foreign Government Obligations
Assets
Investments	193,944	202,706
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Corporate Securities
Assets
Investments	29,890,254	31,156,819
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Residential Mortgage Backed Securities
Assets
Investments	1,346,473	1,512,831
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Commercial Mortgage Backed Securities
Assets
Investments	4,177,242	4,261,227
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Other Asset Backed Securities
Assets
Investments	5,360,405	5,549,849
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Equity Securities
Assets
Investments	2,552
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Assets
Derivative instruments	0	0
Cash and cash equivalents	0	0
Assets	0	0
Liabilities
Fixed index annuities - embedded derivatives	7,680,951	7,938,281
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| United States Government Full Faith and Credit
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| United States Government Sponsored Agencies
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| United States Municipalities, States and Territories
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Foreign Government Obligations
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Corporate Securities
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Residential Mortgage Backed Securities
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Commercial Mortgage Backed Securities
Assets
Investments	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Other Asset Backed Securities
Assets
Investments	0	$ 0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Equity Securities
Assets
Investments	$ 0

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value as of the balance sheet date of the embedded derivative or group of embedded derivatives classified as a liability.

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Fair value portion of investments accounted under the equity method.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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