INVESTMENTS (REPURCHASE TO MATURITY TRANSACTIONS) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Securities sold under agreement to repurchase		$ 1,992
U.S. Treasury, government and agency
Derivative [Line Items]
Securities sold under agreement to repurchase	$ 1,882	1,992
Maturity Overnight and Continuous
Derivative [Line Items]
Securities sold under agreement to repurchase		0
Maturity Overnight and Continuous | U.S. Treasury, government and agency
Derivative [Line Items]
Securities sold under agreement to repurchase	0	0
Maturity Up To 30 Days
Derivative [Line Items]
Securities sold under agreement to repurchase		1,992
Maturity Up To 30 Days | U.S. Treasury, government and agency
Derivative [Line Items]
Securities sold under agreement to repurchase	1,882	1,992
Maturity 30 to 90 Days
Derivative [Line Items]
Securities sold under agreement to repurchase		0
Maturity 30 to 90 Days | U.S. Treasury, government and agency
Derivative [Line Items]
Securities sold under agreement to repurchase	0	0
Maturity Greater than 90 Days
Derivative [Line Items]
Securities sold under agreement to repurchase		0
Maturity Greater than 90 Days | U.S. Treasury, government and agency
Derivative [Line Items]
Securities sold under agreement to repurchase	$ 0	$ 0