INVESTMENTS - Commercial Mortgage and Other Loans by Portfolio Segment (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Commercial Mortgage and Other Loans
Gross commercial mortgage and other loans	$ 7,209	$ 6,946
Valuation allowance	(29)	(27)
Commercial mortgage and other loans	7,180	6,919
Transitional real estate loans
Commercial Mortgage and Other Loans
Gross commercial mortgage and other loans	4,398	4,394
Valuation allowance	(18)	(17)
Commercial mortgage loans
Commercial Mortgage and Other Loans
Gross commercial mortgage and other loans	1,085	1,065
Valuation allowance	(1)	(1)
Middle market loans
Commercial Mortgage and Other Loans
Gross commercial mortgage and other loans	1,726	1,487
Valuation allowance	$ (10)	$ (9)

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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