FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Assets:
Available-for-sale securities	$ 34,056,281	$ 32,723,992
Total fixed maturity securities	36,076,644	34,815,931
Equity securities	716,985	646,027
Other long-term investments	277,724	307,567
Short-term investments	194,299	134,146
Assets related to separate accounts
Variable annuity	12,946,329	12,791,438
Variable universal life	792,200	783,618
Liabilities:
Other liabilities	498,200	457,802
Fixed maturities
Assets:
Available-for-sale securities	33,238,840	32,017,441
Trading securities	2,800,000	2,800,000
Residential mortgage-backed securities
Assets:
Available-for-sale securities	1,438,773	1,445,068
Commercial mortgage-backed securities
Assets:
Available-for-sale securities	1,023,366	970,656
Other asset-backed securities
Assets:
Available-for-sale securities	860,745	871,983
State, municipalities, and political subdivisions
Assets:
Available-for-sale securities	1,523,940	1,410,829
Other government-related securities
Assets:
Available-for-sale securities	51,678	51,427
Corporate bonds
Assets:
Available-for-sale securities	26,829,097	25,759,588
Level 3 | Other asset-backed securities
Assets:
Total investments	548,805	545,808
Level 3 | Corporate bonds
Assets:
Total investments	1,535,409	1,555,898
Measured at fair value on a recurring basis | Level 1
Assets:
Total fixed maturity securities	1,418,039	1,402,580
Equity securities	549,684	523,219
Other long-term investments	71,677	56,469
Short-term investments	182,472	132,543
Total investments	2,221,872	2,114,811
Cash	407,532	466,542
Other assets	11,252	10,979
Assets related to separate accounts
Variable annuity	12,946,329	12,791,438
Variable universal life	792,200	783,618
Total assets	16,379,185	16,167,388
Liabilities:
Other liabilities	24,586	30,241
Total liabilities	24,586	30,241
Measured at fair value on a recurring basis | Level 1 | Fixed maturities
Assets:
Available-for-sale securities	1,214,622	1,211,248
Trading securities	203,417	191,332
Measured at fair value on a recurring basis | Level 1 | U.S. government-related securities
Assets:
Available-for-sale securities	1,214,490	1,211,141
Trading securities	203,417	191,332
Measured at fair value on a recurring basis | Level 1 | Corporate bonds
Assets:
Available-for-sale securities	132	107
Measured at fair value on a recurring basis | Level 2
Assets:
Total fixed maturity securities	32,306,788	31,089,724
Equity securities	85,808	50,927
Other long-term investments	62,239	54,965
Short-term investments	11,827	1,603
Total investments	32,466,662	31,197,219
Assets related to separate accounts
Total assets	32,466,662	31,197,219
Liabilities:
Other liabilities	102,249	156,931
Total liabilities	102,249	156,931
Measured at fair value on a recurring basis | Level 2 | Fixed maturities
Assets:
Available-for-sale securities	29,898,011	28,706,742
Trading securities	2,408,777	2,382,982
Measured at fair value on a recurring basis | Level 2 | Residential mortgage-backed securities
Assets:
Available-for-sale securities	1,438,756	1,445,040
Trading securities	303,729	310,877
Measured at fair value on a recurring basis | Level 2 | Commercial mortgage-backed securities
Assets:
Available-for-sale securities	1,023,366	970,656
Trading securities	160,096	158,570
Measured at fair value on a recurring basis | Level 2 | Other asset-backed securities
Assets:
Available-for-sale securities	311,940	326,175
Trading securities	90,708	93,278
Measured at fair value on a recurring basis | Level 2 | U.S. government-related securities
Assets:
Available-for-sale securities	296,751	296,749
Trading securities	4,973	4,906
Measured at fair value on a recurring basis | Level 2 | State, municipalities, and political subdivisions
Assets:
Available-for-sale securities	1,520,265	1,407,154
Trading securities	274,605	260,892
Measured at fair value on a recurring basis | Level 2 | Other government-related securities
Assets:
Available-for-sale securities	51,678	51,427
Trading securities	55,044	57,097
Measured at fair value on a recurring basis | Level 2 | Corporate bonds
Assets:
Available-for-sale securities	25,255,255	24,209,541
Trading securities	1,519,622	1,497,362
Measured at fair value on a recurring basis | Level 3
Assets:
Total fixed maturity securities	2,351,817	2,323,627
Equity securities	81,493	71,881
Other long-term investments	143,808	196,133
Total investments	2,577,118	2,591,641
Assets related to separate accounts
Total assets	2,577,118	2,591,641
Liabilities:
Annuity account balances	105,593	107,000
Other liabilities	371,365	270,630
Total liabilities	476,958	377,630
Measured at fair value on a recurring basis | Level 3 | Fixed maturities
Assets:
Available-for-sale securities	2,126,207	2,099,451
Trading securities	225,610	224,176
Measured at fair value on a recurring basis | Level 3 | Residential mortgage-backed securities
Assets:
Available-for-sale securities	17	28
Measured at fair value on a recurring basis | Level 3 | Other asset-backed securities
Assets:
Available-for-sale securities	548,805	545,808
Trading securities	194,664	194,977
Measured at fair value on a recurring basis | Level 3 | State, municipalities, and political subdivisions
Assets:
Available-for-sale securities	3,675	3,675
Measured at fair value on a recurring basis | Level 3 | Corporate bonds
Assets:
Available-for-sale securities	1,573,710	1,549,940
Trading securities	30,946	29,199
Measured at fair value on a recurring basis | Fair Values
Assets:
Total fixed maturity securities	36,076,644	34,815,931
Equity securities	716,985	646,027
Other long-term investments	277,724	307,567
Short-term investments	194,299	134,146
Total investments	37,265,652	35,903,671
Cash	407,532	466,542
Other assets	11,252	10,979
Assets related to separate accounts
Variable annuity	12,946,329	12,791,438
Variable universal life	792,200	783,618
Total assets	51,422,965	49,956,248
Liabilities:
Annuity account balances	105,593	107,000
Other liabilities	498,200	457,802
Total liabilities	603,793	564,802
Measured at fair value on a recurring basis | Fair Values | Fixed maturities
Assets:
Available-for-sale securities	33,238,840	32,017,441
Trading securities	2,837,804	2,798,490
Measured at fair value on a recurring basis | Fair Values | Residential mortgage-backed securities
Assets:
Available-for-sale securities	1,438,773	1,445,068
Trading securities	303,729	310,877
Measured at fair value on a recurring basis | Fair Values | Commercial mortgage-backed securities
Assets:
Available-for-sale securities	1,023,366	970,656
Trading securities	160,096	158,570
Measured at fair value on a recurring basis | Fair Values | Other asset-backed securities
Assets:
Available-for-sale securities	860,745	871,983
Trading securities	285,372	288,255
Measured at fair value on a recurring basis | Fair Values | U.S. government-related securities
Assets:
Available-for-sale securities	1,511,241	1,507,890
Trading securities	208,390	196,238
Measured at fair value on a recurring basis | Fair Values | State, municipalities, and political subdivisions
Assets:
Available-for-sale securities	1,523,940	1,410,829
Trading securities	274,605	260,892
Measured at fair value on a recurring basis | Fair Values | Other government-related securities
Assets:
Available-for-sale securities	51,678	51,427
Trading securities	55,044	57,097
Measured at fair value on a recurring basis | Fair Values | Corporate bonds
Assets:
Available-for-sale securities	26,829,097	25,759,588
Trading securities	$ 1,550,568	$ 1,526,561