INVESTMENT OPERATIONS (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investment operations
Investment income before other investment expenses									$ 1,944,740,000	$ 1,889,779,000	$ 1,847,696,000
Other investment expenses									108,552,000	100,441,000	94,252,000
Net investment income	515,340,000	434,772,000	447,064,000	439,012,000	460,784,000	446,374,000	438,648,000	443,532,000	1,836,188,000	1,789,338,000	1,753,444,000
Net realized gains (losses) for all other investments
Fixed maturities									63,161,000	67,669,000	80,044,000
Equity securities									3,276,000	(45,000)	9,136,000
Impairments on fixed maturity securities									(19,100,000)	(58,144,000)	(47,321,000)
Impairments on equity securities									(3,347,000)
Modco trading portfolio									(178,134,000)	177,986,000	164,224,000
Other investments									(9,840,000)	(12,774,000)	(5,651,000)
Total realized gains (losses) - investments									(143,984,000)	174,692,000	200,432,000
Gross realized gains on investments available-for-sale (fixed maturities, equity securities, and short-term investments)									72,600,000	73,200,000	104,500,000
Gross realized losses									27,900,000	60,300,000	62,000,000
Impairment losses on investments available-for-sale									21,700,000	54,700,000	46,600,000
Fair value (proceeds) of securities in an unrealized gain position sold									2,300,000,000	1,600,000,000	2,200,000,000
Gain realized on the sale of securities in an unrealized gain position									72,600,000	73,200,000	104,500,000
Fair value (proceeds) of securities sold in an unrealized loss position									398,200,000	38,000,000	263,100,000
Loss realized on the sale of securities in an unrealized loss position									6,200,000	5,600,000	15,300,000
Fixed maturities
Investment operations
Investment income before other investment expenses									1,508,924,000	1,453,018,000	1,414,965,000
Equity securities
Investment operations
Investment income before other investment expenses									26,735,000	20,740,000	20,595,000
Mortgage loans
Investment operations
Investment income before other investment expenses									333,093,000	349,845,000	336,541,000
Investment real estate
Investment operations
Investment income before other investment expenses									3,555,000	3,289,000	3,458,000
Short-term investments
Investment operations
Investment income before other investment expenses									$ 72,433,000	$ 62,887,000	$ 72,137,000