BENEFITS Benefits - Obligations and Funded Status (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest cost		$ 1	$ 1	$ 1
Fair value of plan assets at beginning of period		126
Fair value of plan assets at end of period		143	126
Other Postretirement Benefits Plan [Member]
Benefit obligation at beginning of period		19	21
Interest cost		1	1
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment					$ 8	$ 0
Actuarial gain		(1)	(1)
Benefit obligation at end of period		25	19	21
Fair value of plan assets at beginning of period		126	118
Return on plan assets and other		11	2
Employer contributions		8	8
Defined Benefit Plan, Benefit Obligation, Benefits Paid		2	2
Fair value of plan assets at end of period		143	126	$ 118
Amount overfunded at end of period (1)	[1]	118	107
Net actuarial gain		(13)	(7)
Prior service cost		20	14
Amounts recognized in accumulated other comprehensive income (pre-tax basis) consist of:		$ 7	$ 7

[1] Recorded as a non-current asset in the consolidated balance sheets.