MORTGAGE LOANS (Details) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 item	Dec. 31, 2012
Mortgage loans
Mortgage loan holdings	$ 4,772,134,000	$ 4,772,134,000	$ 4,948,625,000
Amount that would become due in 2013, if loans are called at their next call dates	106,100,000	106,100,000
Amount that would become due in 2014 through 2018, if loans are called at their next call dates	1,300,000,000	1,300,000,000
Amount that would become due in 2019 through 2023, if loans are called at their next call dates	581,300,000	581,300,000
Amount that would become due after 2023, if loans are called at their next call dates	173,700,000	173,700,000
Allowance for loan and credit losses	7,000,000	7,000,000	2,900,000
Change in the allowance for credit losses
Ending balance	7,000,000	7,000,000	2,900,000
Commercial mortgage loans
Mortgage loans
Mortgage loan holdings	4,800,000,000	4,800,000,000
Allowance for loan and credit losses	7,035,000	7,035,000	2,875,000
Mortgage loans having participation feature	705,700,000	705,700,000	817,300,000
Income recognized on participating mortgage loans	5,800,000	9,200,000
Delinquent mortgage loans, foreclosed properties and restructured loans pursuant to pooling and servicing agreement	16,000,000	16,000,000
Maximum nonperforming mortgage loans, foreclosed properties and restructured loans to invested assets (as a percent)	0.04%	0.04%
Number of loan categories		2
Nonperforming loans not subject to a pooling and servicing agreement	13,800,000	13,800,000
Number of nonperforming loans not subject to a pooling and servicing agreement which have been restructured		0
Loans subject to a pooling and servicing agreement which are nonperforming	2,200,000	2,200,000
Change in the allowance for credit losses
Beginning balance		2,875,000	4,975,000
Charge offs		(2,292,000)	(8,340,000)
Recoveries		(374,000)	(628,000)
Provision		6,826,000	6,868,000
Ending balance	$ 7,035,000	$ 7,035,000	$ 2,875,000
Commercial mortgage loans | Minimum
Mortgage loans
Period for exercise of call options or interest rate reset options		3 years
Commercial mortgage loans | Maximum
Mortgage loans
Period for exercise of call options or interest rate reset options		10 years
Loan-to-value ratio with participating interest (as a percent)	85.00%	85.00%