Annual report pursuant to Section 13 and 15(d)

COMPANY-SPONSORED EMPLOYEE BENEFIT PLANS - Fair Value Measurement of Plan Assets Using Unobservable Inputs (Detail)

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COMPANY-SPONSORED EMPLOYEE BENEFIT PLANS - Fair Value Measurement of Plan Assets Using Unobservable Inputs (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year $ 47,767  
Actual Return on Assets:    
Fair value of plan assets at end of year 54,881 $ 47,767
Fair Value, Inputs, Level 3    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 12 6
Actual Return on Assets:    
Assets Held at End of Year 3 1
Assets Sold During the Year (5) (4)
Purchases 61 11
Sales (6) (2)
Transfers Into (Out of) Level 3 0 0
Fair value of plan assets at end of year 65 12
Fair Value, Inputs, Level 3 | Corporate Bonds    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 0 2
Actual Return on Assets:    
Assets Held at End of Year 0 0
Assets Sold During the Year (5) (4)
Purchases 10 4
Sales (2) (2)
Transfers Into (Out of) Level 3 0 0
Fair value of plan assets at end of year 3 0
Fair Value, Inputs, Level 3 | Other    
Defined Benefit Plan Disclosure [Line Items]    
Fair value of plan assets at beginning of year 12 4
Actual Return on Assets:    
Assets Held at End of Year 3 1
Assets Sold During the Year 0 0
Purchases 51 7
Sales (4) 0
Transfers Into (Out of) Level 3 0 0
Fair value of plan assets at end of year $ 62 $ 12