FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets:
Available-for-sale securities	$ 26,030,303	$ 27,214,682
Trading securities	2,900,000
Total fixed maturity securities	28,304,610	29,769,978
Equity securities	420,505	373,715
Other long-term investments	196,172	130,428
Short-term investments	215,116	216,787
Assets related to separate accounts
Variable annuity	11,921,925	9,601,417
Variable universal life	663,380	562,817
Liabilities:
Other liabilities	427,470	657,874
Fixed maturities
Assets:
Available-for-sale securities	25,521,831	26,762,670
Trading securities	2,800,000	3,000,000
Residential mortgage-backed securities
Assets:
Available-for-sale securities	1,464,027	1,839,330
Commercial mortgage-backed securities
Assets:
Available-for-sale securities	911,607	869,823
Other asset-backed securities
Assets:
Available-for-sale securities	877,164	975,013
U.S. government-related securities
Assets:
Available-for-sale securities	1,213,436	1,168,446
States, municipals, and political subdivisions
Assets:
Available-for-sale securities	1,300,321	1,443,653
Other government-related securities
Assets:
Available-for-sale securities	41,128	100,778
Corporate bonds
Assets:
Available-for-sale securities	19,714,148	20,365,627
Measured at fair value on a recurring basis | Level 1
Assets:
Total fixed maturity securities	1,262,408	1,214,899
Equity securities	311,637	273,072
Other long-term investments	58,567	23,639
Short-term investments	212,816	214,295
Total investments	1,845,428	1,725,905
Cash	229,747	269,582
Assets related to separate accounts
Variable annuity	11,921,925	9,601,417
Variable universal life	663,380	562,817
Total assets	14,660,480	12,159,721
Liabilities:
Other liabilities	11,304	19,187
Total liabilities	11,304	19,187
Measured at fair value on a recurring basis | Level 1 | Fixed maturities
Assets:
Available-for-sale securities	1,063,691	910,195
Trading securities	198,717	304,704
Measured at fair value on a recurring basis | Level 1 | U.S. government-related securities
Assets:
Available-for-sale securities	1,063,584	909,988
Trading securities	198,717	304,704
Measured at fair value on a recurring basis | Level 1 | Corporate bonds
Assets:
Available-for-sale securities	107	207
Measured at fair value on a recurring basis | Level 2
Assets:
Total fixed maturity securities	26,125,571	27,696,104
Equity securities	43,341	35,116
Other long-term investments	54,600	58,134
Short-term investments	2,300	2,492
Total investments	26,225,812	27,791,846
Assets related to separate accounts
Total assets	26,225,812	27,791,846
Liabilities:
Other liabilities	185,443	27,250
Total liabilities	185,443	27,250
Measured at fair value on a recurring basis | Level 2 | Fixed maturities
Assets:
Available-for-sale securities	23,717,568	25,064,150
Trading securities	2,408,003	2,631,954
Measured at fair value on a recurring basis | Level 2 | Residential mortgage-backed securities
Assets:
Available-for-sale securities	1,463,989	1,839,326
Trading securities	308,356	357,803
Measured at fair value on a recurring basis | Level 2 | Commercial mortgage-backed securities
Assets:
Available-for-sale securities	911,607	869,823
Trading securities	169,046	171,073
Measured at fair value on a recurring basis | Level 2 | Other asset-backed securities
Assets:
Available-for-sale securities	328,393	378,870
Trading securities	90,726	87,395
Measured at fair value on a recurring basis | Level 2 | U.S. government-related securities
Assets:
Available-for-sale securities	149,852	258,458
Trading securities	5,147	1,169
Measured at fair value on a recurring basis | Level 2 | States, municipals, and political subdivisions
Assets:
Available-for-sale securities	1,296,046	1,439,378
Trading securities	262,036	278,898
Measured at fair value on a recurring basis | Level 2 | Other government-related securities
Assets:
Available-for-sale securities	41,128	80,767
Trading securities	57,525	63,444
Measured at fair value on a recurring basis | Level 2 | Corporate bonds
Assets:
Available-for-sale securities	19,526,553	20,197,528
Trading securities	1,515,167	1,672,172
Measured at fair value on a recurring basis | Level 3
Assets:
Total fixed maturity securities	916,631	858,975
Equity securities	65,527	65,527
Other long-term investments	83,005	48,655
Total investments	1,065,163	973,157
Assets related to separate accounts
Total assets	1,065,163	973,157
Liabilities:
Annuity account balances	110,590	129,468
Other liabilities	230,723	611,437
Total liabilities	341,313	740,905
Measured at fair value on a recurring basis | Level 3 | Fixed maturities
Assets:
Available-for-sale securities	740,572	788,325
Trading securities	176,059	70,650
Measured at fair value on a recurring basis | Level 3 | Residential mortgage-backed securities
Assets:
Available-for-sale securities	38	4
Measured at fair value on a recurring basis | Level 3 | Other asset-backed securities
Assets:
Available-for-sale securities	548,771	596,143
Trading securities	170,967	70,535
Measured at fair value on a recurring basis | Level 3 | States, municipals, and political subdivisions
Assets:
Available-for-sale securities	4,275	4,275
Measured at fair value on a recurring basis | Level 3 | Other government-related securities
Assets:
Available-for-sale securities		20,011
Measured at fair value on a recurring basis | Level 3 | Corporate bonds
Assets:
Available-for-sale securities	187,488	167,892
Trading securities	5,092	115
Measured at fair value on a recurring basis | Total
Assets:
Total fixed maturity securities	28,304,610	29,769,978
Equity securities	420,505	373,715
Other long-term investments	196,172	130,428
Short-term investments	215,116	216,787
Total investments	29,136,403	30,490,908
Cash	229,747	269,582
Assets related to separate accounts
Variable annuity	11,921,925	9,601,417
Variable universal life	663,380	562,817
Total assets	41,951,455	40,924,724
Liabilities:
Annuity account balances	110,590	129,468
Other liabilities	427,470	657,874
Total liabilities	538,060	787,342
Measured at fair value on a recurring basis | Total | Fixed maturities
Assets:
Available-for-sale securities	25,521,831	26,762,670
Trading securities	2,782,779	3,007,308
Measured at fair value on a recurring basis | Total | Residential mortgage-backed securities
Assets:
Available-for-sale securities	1,464,027	1,839,330
Trading securities	308,356	357,803
Measured at fair value on a recurring basis | Total | Commercial mortgage-backed securities
Assets:
Available-for-sale securities	911,607	869,823
Trading securities	169,046	171,073
Measured at fair value on a recurring basis | Total | Other asset-backed securities
Assets:
Available-for-sale securities	877,164	975,013
Trading securities	261,693	157,930
Measured at fair value on a recurring basis | Total | U.S. government-related securities
Assets:
Available-for-sale securities	1,213,436	1,168,446
Trading securities	203,864	305,873
Measured at fair value on a recurring basis | Total | States, municipals, and political subdivisions
Assets:
Available-for-sale securities	1,300,321	1,443,653
Trading securities	262,036	278,898
Measured at fair value on a recurring basis | Total | Other government-related securities
Assets:
Available-for-sale securities	41,128	100,778
Trading securities	57,525	63,444
Measured at fair value on a recurring basis | Total | Corporate bonds
Assets:
Available-for-sale securities	19,714,148	20,365,627
Trading securities	$ 1,520,259	$ 1,672,287