INVESTMENT OPERATIONS (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	$ 24,104,126,000	$ 23,451,332,000
Gross Unrealized Gains	3,251,213,000	2,284,621,000
Gross Unrealized Losses	(140,657,000)	(447,352,000)
Fair Value	27,214,682,000	25,288,601,000
Total OTTI Recognized in OCI	(6,135,000)	(52,498,000)
Amortized cost and fair value of the Company's investments classified as held-to-maturity
Fair Value	319,163,000
Amortized Cost
Due in one year or less	452,876,000
Due after one year through five years	4,568,417,000
Due after five years through ten years	6,283,158,000
Due after ten years	12,349,551,000
Total	23,654,002,000
Fair Value
Due in one year or less	459,845,000
Due after one year through five years	4,996,310,000
Due after five years through ten years	6,967,782,000
Due after ten years	14,338,733,000
Total	26,762,670,000
Amortized Cost
Due after ten years	300,000,000
Total	300,000,000
Fair Value
Due after ten years	319,163,000
Total	319,163,000
Fixed maturities:
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	23,654,002,000	23,149,166,000
Gross Unrealized Gains	3,239,332,000	2,279,191,000
Gross Unrealized Losses	(130,664,000)	(430,757,000)
Fair Value	26,762,670,000	24,997,600,000
Total OTTI Recognized in OCI	(6,135,000)	(52,424,000)
Amortized cost and fair value of the Company's investments classified as held-to-maturity
Amortized Cost	300,000,000
Gross Unrealized Gains	19,163,000
Fair Value	319,163,000
Trading securities	3,000,000,000	3,000,000,000
Residential mortgage-backed securities
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	1,766,260,000	2,340,172,000
Gross Unrealized Gains	92,417,000	82,574,000
Gross Unrealized Losses	(19,347,000)	(85,702,000)
Fair Value	1,839,330,000	2,337,044,000
Total OTTI Recognized in OCI	(406,000)	(47,652,000)
Commercial mortgage-backed securities
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	797,844,000	530,283,000
Gross Unrealized Gains	72,577,000	24,473,000
Gross Unrealized Losses	(598,000)	(4,229,000)
Fair Value	869,823,000	550,527,000
Other asset-backed securities
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	1,023,649,000	997,398,000
Gross Unrealized Gains	12,788,000	6,529,000
Gross Unrealized Losses	(61,424,000)	(90,898,000)
Fair Value	975,013,000	913,029,000
Total OTTI Recognized in OCI	(241,000)	(6,559,000)
U.S. government-related securities
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	1,097,501,000	1,150,525,000
Gross Unrealized Gains	71,536,000	65,212,000
Gross Unrealized Losses	(591,000)	(58,000)
Fair Value	1,168,446,000	1,215,679,000
Other government-related securities
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	93,565,000	88,058,000
Gross Unrealized Gains	7,258,000	4,959,000
Gross Unrealized Losses	(45,000)
Fair Value	100,778,000	93,017,000
States, municipals, and political subdivisions
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	1,188,019,000	1,154,307,000
Gross Unrealized Gains	255,898,000	173,406,000
Gross Unrealized Losses	(264,000)
Fair Value	1,443,653,000	1,327,713,000
Corporate bonds
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	17,687,164,000	16,888,423,000
Gross Unrealized Gains	2,726,858,000	1,922,038,000
Gross Unrealized Losses	(48,395,000)	(249,870,000)
Fair Value	20,365,627,000	18,560,591,000
Total OTTI Recognized in OCI	(5,488,000)	1,787,000
Other
Amortized cost and fair value of the Company's investments classified as held-to-maturity
Amortized Cost	300,000,000
Gross Unrealized Gains	19,163,000
Fair Value	319,163,000
Equity securities
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	352,272,000	286,537,000
Gross Unrealized Gains	11,881,000	5,430,000
Gross Unrealized Losses	(9,993,000)	(16,595,000)
Fair Value	354,160,000	275,372,000
Total OTTI Recognized in OCI		(74,000)
Amortized cost and fair value of the Company's investments classified as held-to-maturity
Trading securities	19,600,000	17,000,000
Short-term investments
Amortized cost and fair value of the Company's investments classified as available-for-sale
Amortized Cost	97,852,000	15,629,000
Fair Value	97,852,000	15,629,000
Amortized cost and fair value of the Company's investments classified as held-to-maturity
Trading securities	$ 118,900,000	$ 85,800,000