Fair Values of Financial Instruments (Fair Value by Balance Sheet Grouping) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
ASSETS
Debt securities held to maturity	$ 7,537,665	$ 7,228,268
Debt securities, available for sale	3,409,466	2,946,059
Derivatives, index options	106,364	14,684
Equity securities	19,462	17,491
Carrying Values
ASSETS
Debt securities held to maturity	7,224,459	7,285,254
Debt securities, available for sale	3,409,466	2,946,059
Cash and cash equivalents	171,509	131,976
Mortgage loans	224,048	203,180
Policy loans	80,272	54,724
Other loans	13,864	12,272
Derivatives, index options	106,364	14,684
Equity securities	19,462	17,491
Life interest in Libbie Shearn Moody Trust	8,692	8,692
LIABILITIES
Deferred annuity contracts	7,087,363	7,455,642
Immediate annuity and supplemental contracts	405,516	407,413
Contingent consideration on businesses acquired	3,965
Fair Values
ASSETS
Debt securities held to maturity	7,537,665	7,228,268
Debt securities, available for sale	3,409,466	2,946,059
Cash and cash equivalents	171,509	131,976
Mortgage loans	227,159	202,762
Policy loans	127,874	90,802
Other loans	14,028	12,709
Derivatives, index options	106,364	14,684
Equity securities	19,462	17,491
Life interest in Libbie Shearn Moody Trust	12,775	12,775
LIABILITIES
Deferred annuity contracts	5,827,205	6,403,007
Immediate annuity and supplemental contracts	432,789	415,726
Contingent consideration on businesses acquired	3,965
Level 1
ASSETS
Debt securities held to maturity	0	0
Debt securities, available for sale	0	0
Cash and cash equivalents	171,509	131,976
Mortgage loans	0	0
Policy loans	0	0
Other loans	0	0
Derivatives, index options	0	0
Equity securities	19,462	17,491
Life interest in Libbie Shearn Moody Trust	0	0
LIABILITIES
Deferred annuity contracts	0	0
Immediate annuity and supplemental contracts	0	0
Contingent consideration on businesses acquired	0
Level 2
ASSETS
Debt securities held to maturity	7,536,101	7,226,362
Debt securities, available for sale	3,409,466	2,946,059
Cash and cash equivalents	0	0
Mortgage loans	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
LIABILITIES
Deferred annuity contracts	0	0
Immediate annuity and supplemental contracts	0	0
Contingent consideration on businesses acquired	0
Level 3
ASSETS
Debt securities held to maturity	1,564	1,906
Debt securities, available for sale	0	0
Cash and cash equivalents	0	0
Mortgage loans	227,159	202,762
Policy loans	127,874	90,802
Other loans	14,028	12,709
Derivatives, index options	106,364	14,684
Equity securities	0	0
Life interest in Libbie Shearn Moody Trust	12,775	12,775
LIABILITIES
Deferred annuity contracts	5,827,205	6,403,007
Immediate annuity and supplemental contracts	432,789	$ 415,726
Contingent consideration on businesses acquired	$ 3,965

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