BASIS OF PRESENTATION - Intangible Assets Summary (Details) - USD ($)
$ in Millions
Mar. 31, 2018
Dec. 31, 2017
Other intangible assets    
Gross Carrying Amount $ 2,712 $ 2,649
Accumulated Amortization (920) (883)
Net Book Value 1,792 1,766
Capitalized software costs    
Other intangible assets    
Gross Carrying Amount 1,644 1,582
Accumulated Amortization (784) (754)
Net Book Value 860 828
Trade names    
Other intangible assets    
Gross Carrying Amount 102 102
Accumulated Amortization 0 0
Net Book Value 102 102
Contracts    
Other intangible assets    
Gross Carrying Amount 860 859
Accumulated Amortization (64) (60)
Net Book Value 796 799
Other    
Other intangible assets    
Gross Carrying Amount 106 106
Accumulated Amortization (72) (69)
Net Book Value $ 34 $ 37