Fair Values of Financial Instruments - Fair Value by Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
ASSETS
Debt securities, available-for-sale	$ 10,014,351	$ 10,770,923
Debt securities, trading	654,333	0
Derivatives, index options	137,130	132,821
Equity securities	19,120	17,744
Carrying Values
ASSETS
Debt securities, available-for-sale	10,014,351	10,770,923
Debt securities, trading	654,333
Cash and cash equivalents	435,644	581,059
Mortgage loans	377,495	332,521
Real estate	33,639	33,783
Policy loans	72,832	74,083
Other loans	26,800	23,396
Derivatives, index options	137,130	132,821
Equity securities	19,120	17,744
Life interest in Libbie Shearn Moody Trust	9,083	9,083
Other investments	4,513	4,513
LIABILITIES
Deferred annuity contracts	6,605,094	6,662,730
Immediate annuity and supplemental contracts	416,773	412,526
Fair Values
ASSETS
Debt securities, available-for-sale	10,014,351	10,770,923
Debt securities, trading	654,333
Cash and cash equivalents	435,644	581,059
Mortgage loans	393,129	348,175
Real estate	51,627	48,577
Policy loans	109,588	121,260
Other loans	27,102	23,691
Derivatives, index options	137,130	132,821
Equity securities	19,120	17,744
Life interest in Libbie Shearn Moody Trust	12,775	12,775
Other investments	24,852	22,580
LIABILITIES
Deferred annuity contracts	5,327,510	5,192,663
Immediate annuity and supplemental contracts	457,299	467,538
Level 1
ASSETS
Debt securities, available-for-sale	0	0
Debt securities, trading	0
Cash and cash equivalents	435,644	581,059
Mortgage loans	0	0
Real estate	0	0
Policy loans	0	0
Other loans	0	0
Derivatives, index options	0	0
Equity securities	19,120	17,744
Life interest in Libbie Shearn Moody Trust	0	0
Other investments	0	0
LIABILITIES
Deferred annuity contracts	0	0
Immediate annuity and supplemental contracts	0	0
Level 2
ASSETS
Debt securities, available-for-sale	10,014,351	10,770,923
Debt securities, trading	654,333
Cash and cash equivalents	0	0
Mortgage loans	0	0
Real estate	0	0
Policy loans	0	0
Other loans	0	0
Derivatives, index options	0	0
Equity securities	0	0
Life interest in Libbie Shearn Moody Trust	0	0
Other investments	0	0
LIABILITIES
Deferred annuity contracts	0	0
Immediate annuity and supplemental contracts	0	0
Level 3
ASSETS
Debt securities, available-for-sale	0	0
Debt securities, trading	0
Cash and cash equivalents	0	0
Mortgage loans	393,129	348,175
Real estate	51,627	48,577
Policy loans	109,588	121,260
Other loans	27,102	23,691
Derivatives, index options	137,130	132,821
Equity securities	0	0
Life interest in Libbie Shearn Moody Trust	12,775	12,775
Other investments	24,852	22,580
LIABILITIES
Deferred annuity contracts	5,327,510	5,192,663
Immediate annuity and supplemental contracts	$ 457,299	$ 467,538

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