Fair Values of Financial Instruments - Schedule of Carrying Amounts and Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Debt securities, held-to-maturity	$ 0	$ 7,407,703
Debt securities, available-for-sale	10,770,923	3,356,945
Derivatives, index options	132,821	157,588
Equity securities	17,744	23,594
Restatement Adjustment
LIABILITIES
Future policy benefits		15,000
Carrying Values
ASSETS
Debt securities, held-to-maturity		7,106,245
Debt securities, available-for-sale	10,770,923	3,356,945
Cash and cash equivalents	581,059	253,524
Mortgage loans	332,521	272,422
Real estate	33,783	34,588
Policy loans	74,083	80,008
Other loans	23,396	13,547
Derivatives, index options	132,821	157,588
Equity securities	17,744	23,594
Life interest in Libbie Shearn Moody Trust	9,083	9,230
Other invested assets	4,513	197
LIABILITIES
Deferred annuity contracts	6,662,730	7,014,833
Immediate annuity and supplemental contracts	412,526	400,465
Contingent consideration on businesses acquired	0	4,076
Fair Values
ASSETS
Debt securities, held-to-maturity		7,407,703
Debt securities, available-for-sale	10,770,923	3,356,945
Cash and cash equivalents	581,059	253,524
Mortgage loans	348,175	270,931
Real estate	48,577	57,204
Policy loans	121,260	123,650
Other loans	23,691	13,698
Derivatives, index options	132,821	157,588
Equity securities	17,744	23,594
Life interest in Libbie Shearn Moody Trust	12,775	12,775
Other invested assets	22,580	16,182
LIABILITIES
Deferred annuity contracts	5,192,663	5,931,352
Immediate annuity and supplemental contracts	467,538	422,931
Contingent consideration on businesses acquired	0	4,076
Level 1
ASSETS
Debt securities, held-to-maturity		0
Debt securities, available-for-sale	0	0
Cash and cash equivalents	581,059	253,524
Mortgage loans	0	0
Real estate	0	0
Policy loans	0	0
Other loans	0	0
Derivatives, index options	0	0
Equity securities	17,744	23,594
Life interest in Libbie Shearn Moody Trust	0	0
Other invested assets		2
LIABILITIES
Deferred annuity contracts	0	0
Immediate annuity and supplemental contracts	0	0
Contingent consideration on businesses acquired	0	0
Level 2
ASSETS
Debt securities, held-to-maturity		7,407,703
Debt securities, available-for-sale	10,770,923	3,356,945
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 invested assets	0	0
LIABILITIES
Deferred annuity contracts	0	0
Immediate annuity and supplemental contracts	0	0
Contingent consideration on businesses acquired	0	0
Level 3
ASSETS
Debt securities, held-to-maturity		0
Debt securities, available-for-sale	0	0
Cash and cash equivalents	0	0
Mortgage loans	348,175	270,931
Real estate	48,577	57,204
Policy loans	121,260	123,650
Other loans	23,691	13,698
Derivatives, index options	132,821	157,588
Equity securities	0	0
Life interest in Libbie Shearn Moody Trust	12,775	12,775
Other invested assets	22,580	16,180
LIABILITIES
Deferred annuity contracts	5,192,663	5,931,352
Immediate annuity and supplemental contracts	467,538	422,931
Contingent consideration on businesses acquired	$ 0	$ 4,076