FAIR VALUE OF FINANCIAL INSTRUMENTS - Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets:
Mortgage loans on real estate	$ 9,379,401	$ 7,724,733
Policy loans	1,675,121	1,695,886
Fixed maturities, held-to-maturity	2,823,881	2,633,474
Other long-term investments	2,479,520	798,342
Liabilities:
Stable value product account balances	5,443,752	5,234,731
Future policy benefits and claims	14,289,907	13,720,081
Other policyholders’ funds	1,576,856	1,128,379
Debt
Non-recourse funding obligations	3,082,753	2,888,329
Capital lease obligations	1,000
Capital lease obligations		1,300
Carrying Amounts
Assets:
Mortgage loans on real estate	9,379,401	7,724,733
Policy loans	1,675,121	1,695,886
Fixed maturities, held-to-maturity	2,823,881	2,633,474
Other long-term investments	1,216,996	0
Liabilities:
Future policy benefits and claims	1,701,324	1,671,414
Other policyholders’ funds	127,084	131,150
Debt
Non-recourse funding obligations	3,082,753	2,888,329
Carrying Amounts \| Golden Gate and Golden Gate V
Debt
Non-recourse funding obligations		2,600,000
Carrying Amounts \| Level 3
Debt
Subordinated Debt Obligations, Fair Value Disclosure	110,000	110,000
Carrying Amounts \| Level 3 \| Golden Gate and Golden Gate V
Debt
Non-recourse funding obligations	2,800,000
Fair Value \| Level 3
Assets:
Mortgage loans on real estate	9,584,487	7,447,702
Policy loans	1,675,121	1,695,886
Fixed maturities, held-to-maturity	3,025,790	2,547,210
Other long-term investments	1,246,889	0
Liabilities:
Stable value product account balances	5,551,195	5,200,723
Future policy benefits and claims	1,705,235	1,671,434
Other policyholders’ funds	130,259	131,782
Debt
Non-recourse funding obligations	3,298,580	2,801,399
Subordinated Debt Obligations, Fair Value Disclosure	113,286	95,476
Fair Value \| Level 3 \| Golden Gate and Golden Gate V
Debt
Non-recourse funding obligations	$ 3,000,000	$ 2,500,000

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Non-recourse funding obligations issued by special purpose entities owned by the reporting entity. The funding obligations are direct financial obligations of the special purpose entity and are not guaranteed by the reporting entity.

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Present value of lessee's discounted obligation for lease payments from finance lease.

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Amount of investment in debt security measured at amortized cost (held-to-maturity).

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Amount before allowance of loans made to policy and contract holders using their life insurance contracts' cash value or separate accounts as collateral. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums over and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

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