Annual report pursuant to Section 13 and 15(d)

BENEFIT PLANS - Fair Value of Plan Assets (Details)

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BENEFIT PLANS - Fair Value of Plan Assets (Details) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Aug. 16, 2016
Summary of plan assets investments      
Fair value of plan assets $ 903 $ 841  
Fair value of plan assets, Percentage 100.00% 100.00%  
Mutual Funds-money market      
Summary of plan assets investments      
Fair value of plan assets $ 14 $ 21  
Fair value of plan assets, Percentage 2.00% 3.00%  
U.S. Treasury securities      
Summary of plan assets investments      
Fair value of plan assets $ 5 $ 0  
Fair value of plan assets, Percentage 1.00% 0.00%  
Corporate obligations      
Summary of plan assets investments      
Fair value of plan assets $ 293 $ 218  
Fair value of plan assets, Percentage 32.00% 26.00%  
U.S. Government obligations      
Summary of plan assets investments      
Fair value of plan assets $ 216 $ 165  
Fair value of plan assets, Percentage 24.00% 19.00%  
Mutual funds-fixed income      
Summary of plan assets investments      
Fair value of plan assets $ 0 $ 51  
Fair value of plan assets, Percentage 0.00% 6.00%  
U.S. Government Agencies      
Summary of plan assets investments      
Fair value of plan assets $ 23 $ 10  
Fair value of plan assets, Percentage 3.00% 1.00%  
Mutual funds-equities      
Summary of plan assets investments      
Fair value of plan assets $ 118 $ 150  
Fair value of plan assets, Percentage 13.00% 18.00%  
Common stock      
Summary of plan assets investments      
Fair value of plan assets $ 158 $ 182  
Fair value of plan assets, Percentage 17.00% 22.00%  
Preferred stock      
Summary of plan assets investments      
Fair value of plan assets $ 5 $ 5  
Fair value of plan assets, Percentage 1.00% 1.00%  
Exchange Traded Funds      
Summary of plan assets investments      
Fair value of plan assets $ 58 $ 28  
Fair value of plan assets, Percentage 6.00% 3.00%  
Limited Partnerships      
Summary of plan assets investments      
Fair value of plan assets $ 13 $ 11  
Fair value of plan assets, Percentage 1.00% 1.00%  
FirstMerit Bank      
Summary of plan assets investments      
Fair value of plan assets     $ 280