INSURANCE LIABILITIES - Investment in Variable Insurance Trust Mutual Funds (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
GMDB
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Investment in Variable Insurance Trust Mutual Funds	$ 92,504	$ 94,672
GMDB | Equity
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Investment in Variable Insurance Trust Mutual Funds	76,532	78,069
GMDB | Fixed income
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Investment in Variable Insurance Trust Mutual Funds	2,165	2,234
GMDB | Balanced
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Investment in Variable Insurance Trust Mutual Funds	13,525	14,084
GMDB | Other
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Investment in Variable Insurance Trust Mutual Funds	282	285
GMIB
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Investment in Variable Insurance Trust Mutual Funds	60,459	62,286
GMIB | Equity
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Investment in Variable Insurance Trust Mutual Funds	49,042	50,429
GMIB | Fixed income
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Investment in Variable Insurance Trust Mutual Funds	1,528	1,568
GMIB | Balanced
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Investment in Variable Insurance Trust Mutual Funds	9,762	10,165
GMIB | Other
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Investment in Variable Insurance Trust Mutual Funds	$ 127	$ 124