FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets:
Available-for-sale securities	$ 26,090,742	$ 27,271,759
Total fixed maturity securities	28,323,215	29,787,959
Equity securities	461,231	411,786
Other long-term investments	266,730	113,364
Short-term investments	216,224	217,812
Assets related to separate accounts
Variable annuity	11,921,925	9,601,417
Variable universal life	663,380	562,817
Liabilities:
Other liabilities	434,232	657,874
Fixed maturities
Assets:
Available-for-sale securities	25,540,436	26,780,651
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
State, municipalities, and political subdivisions
Assets:
Available-for-sale securities	1,300,377	1,443,713
Other government-related securities
Assets:
Available-for-sale securities	41,128	100,778
Corporate bonds
Assets:
Available-for-sale securities	19,732,697	20,382,051
Level 3 | Other asset-backed securities
Assets:
Total investments	548,711	596,143
Level 3 | Other government-related securities
Assets:
Total investments		20,011
Level 3 | Corporate bonds
Assets:
Total investments	192,580	168,007
Measured at fair value on a recurring basis | Level 1
Assets:
Total fixed maturity securities	1,262,408	1,214,899
Equity securities	348,472	307,252
Other long-term investments	58,567	23,639
Short-term investments	213,924	215,320
Total investments	1,883,371	1,761,110
Cash	354,449	368,801
Other assets	10,086	8,239
Assets related to separate accounts
Variable annuity	11,921,925	9,601,417
Variable universal life	663,380	562,817
Total assets	14,833,211	12,302,384
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	26,144,121	27,714,025
Equity securities	43,341	35,116
Other long-term investments	54,600	58,134
Short-term investments	2,300	2,492
Total investments	26,244,362	27,809,767
Assets related to separate accounts
Total assets	26,244,362	27,809,767
Liabilities:
Other liabilities	136,398	27,250
Total liabilities	136,398	27,250
Measured at fair value on a recurring basis | Level 2 | Fixed maturities
Assets:
Available-for-sale securities	23,736,118	25,082,071
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	259,955
Trading securities	5,147	1,169
Measured at fair value on a recurring basis | Level 2 | State, municipalities, and political subdivisions
Assets:
Available-for-sale securities	1,296,047	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	19,545,102	20,213,952
Trading securities	1,515,167	1,672,172
Measured at fair value on a recurring basis | Level 3
Assets:
Total fixed maturity securities	916,686	859,035
Equity securities	69,418	69,418
Other long-term investments	153,563	31,591
Total investments	1,139,667	960,044
Assets related to separate accounts
Total assets	1,139,667	960,044
Liabilities:
Annuity account balances	110,590	129,468
Other liabilities	286,530	611,437
Total liabilities	397,120	740,905
Measured at fair value on a recurring basis | Level 3 | Fixed maturities
Assets:
Available-for-sale securities	740,627	788,385
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 | State, municipalities, and political subdivisions
Assets:
Available-for-sale securities	4,330	4,335
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 | Fair Values
Assets:
Total fixed maturity securities	28,323,215	29,787,959
Equity securities	461,231	411,786
Other long-term investments	266,730	113,364
Short-term investments	216,224	217,812
Total investments	29,267,400	30,530,921
Cash	354,449	368,801
Other assets	10,086	8,239
Assets related to separate accounts
Variable annuity	11,921,925	9,601,417
Variable universal life	663,380	562,817
Total assets	42,217,240	41,072,195
Liabilities:
Annuity account balances	110,590	129,468
Other liabilities	434,232	657,874
Total liabilities	544,822	787,342
Measured at fair value on a recurring basis | Fair Values | Fixed maturities
Assets:
Available-for-sale securities	25,540,436	26,780,651
Trading securities	2,782,779	3,007,308
Measured at fair value on a recurring basis | Fair Values | 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 | Fair Values | 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 | Fair Values | 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 | Fair Values | U.S. government-related securities
Assets:
Available-for-sale securities	1,213,436	1,169,943
Trading securities	203,864	305,873
Measured at fair value on a recurring basis | Fair Values | State, municipalities, and political subdivisions
Assets:
Available-for-sale securities	1,300,377	1,443,713
Trading securities	262,036	278,898
Measured at fair value on a recurring basis | Fair Values | 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 | Fair Values | Corporate bonds
Assets:
Available-for-sale securities	19,732,697	20,382,051
Trading securities	$ 1,520,259	$ 1,672,287