FAIR VALUE OF FINANCIAL INSTRUMENTS (Details 2) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Determination of fair values
Number of primary sources of information used for determining fair value	1
Total number of primary sources of information available for determining fair value	3
Minimum percentage of the Company's fixed maturity securities priced by third party pricing services	90.00%
Number of independent non-binding broker quotes obtained per security	1
Percentage of derivatives excluding embedded derivatives that were priced using exchange prices or independent broker quotations	79.90%
Policy liabilities (net of policy loans)	2,700,000,000
Fair value of the trading securities	3,100,000,000
Other long-term investments	152,882,000	130,428,000
Annuity account balances
Fixed indexed annuities, discount rate for one month (as a percent)	0.33%
Fixed indexed annuities, discount rate for five years (as a percent)	1.91%
Fixed indexed annuities, discount rate for thirty years (as a percent)	4.28%
Interest support, YRT premium support and portfolio maintenance agreement
Determination of fair values
Other long-term investments	13,300,000
Golden Gate II Captive Insurance Company (Golden Gate II) | Interest Support Agreement
Determination of fair values
Other long-term investments	11,100,000
Golden Gate II Captive Insurance Company (Golden Gate II) | YRT premium support agreement
Determination of fair values
Other long-term investments	1,700,000
Golden Gate V and West Coast Life | Portfolio maintenance agreements
Determination of fair values
Other long-term investments	500,000
Level 3 | Trading Securities
Determination of fair values
Carrying amount	71,400,000
Percentage of underlying collateral of student-loan backed auction rate securities guaranteed by the Federal Family Education Loan Program ("FFELP"), minimum	97.00%
Asset-Backed Securities | Level 2
Determination of fair values
Carrying amount	3,600,000,000
Asset-Backed Securities | Level 3
Determination of fair values
Carrying amount	632,100,000
Other asset-backed securities
Determination of fair values
Percentage of underlying collateral of student-loan backed auction rate securities guaranteed by the Federal Family Education Loan Program ("FFELP"), minimum	97.00%	97.00%
Corporate bonds, U.S. Government-related securities, States, municipals, and political subdivisions, and Other government related securities | Level 2
Determination of fair values
Carrying amount	24,300,000,000
Corporate bonds, U.S. Government-related securities, States, municipals, and political subdivisions, and Other government related securities | Level 3
Determination of fair values
Carrying amount	153,900,000
Equity securities | Level 2 and Level 3
Determination of fair values
Carrying amount	102,600,000
FHLB stock	64,600,000
Equity securities | Level 3
Determination of fair values
FHLB stock	65,500,000	65,500,000
Embedded derivative - GMWB
Determination of fair values
Mortality (as a percent)	57.00%