Fair Values of Financial Instruments (Fair Value by Balance Sheet Grouping) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
ASSETS
Securities held to maturity	$ 7,195,441	$ 6,656,144
Securities available for sale	2,724,880	2,651,544
Derivatives, index options	109,812	169,314
Fair Values [Member]
ASSETS
Securities held to maturity	7,195,441	6,656,144
Securities available for sale	2,724,880	2,651,544
Cash and short-term investments	121,482	120,859
Mortgage loans	159,845	138,159
Policy loans	63,746	65,969
Other loans	2,462	3,143
Derivatives, index options	109,812	169,314
Life interest in Libbie Shearn Moody Trust	12,775	12,775
LIABILITIES
Deferred annuity contracts	7,102,374	6,941,902
Immediate annuity and supplemental contracts	472,485	483,690
Carrying Values [Member]
ASSETS
Securities held to maturity	6,898,038	6,510,320
Securities available for sale	2,724,880	2,651,544
Cash and short-term investments	121,482	120,859
Mortgage loans	152,740	132,765
Policy loans	63,746	65,969
Other loans	2,318	2,986
Derivatives, index options	109,812	169,314
Life interest in Libbie Shearn Moody Trust	0	0
LIABILITIES
Deferred annuity contracts	7,471,884	7,288,861
Immediate annuity and supplemental contracts	448,892	463,276
Level 1 [Member]
ASSETS
Securities held to maturity	0	0
Securities available for sale	16,405	13,802
Cash and short-term investments	121,482	120,859
Mortgage loans	0	0
Policy loans	0	0
Other loans	0	0
Derivatives, index options	0	0
Life interest in Libbie Shearn Moody Trust	0	0
LIABILITIES
Deferred annuity contracts	0	0
Immediate annuity and supplemental contracts	0	0
Level 2 [Member]
ASSETS
Securities held to maturity	7,195,441	6,656,144
Securities available for sale	2,708,475	2,637,742
Cash and short-term investments	0	0
Mortgage loans	0	0
Policy loans	0	0
Other loans	0	0
Derivatives, index options	0	0
Life interest in Libbie Shearn Moody Trust	0	0
LIABILITIES
Deferred annuity contracts	0	0
Immediate annuity and supplemental contracts	0	0
Level 3 [Member]
ASSETS
Securities held to maturity	0	0
Securities available for sale	0	0
Cash and short-term investments	0	0
Mortgage loans	159,845	138,159
Policy loans	63,746	65,969
Other loans	2,462	3,143
Derivatives, index options	109,812	169,314
Life interest in Libbie Shearn Moody Trust	12,775	12,775
LIABILITIES
Deferred annuity contracts	7,102,374	6,941,902
Immediate annuity and supplemental contracts	$ 472,485	$ 483,690