v3.20.2
Accumulated Other Comprehensive Income​ (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Apr. 01, 2020
AOCI Attributable to Parent [Abstract]          
Balance at beginning of period $ 1,389 $ 3,117 $ 2,973 $ 2,969  
Separation-related adjustments (A) (8)   (324)    
Other comprehensive income:          
Foreign currency translation 37 45 42 59  
Total Other comprehensive income, net of tax 80 46 139 60  
Balance at end of period 1,488 3,003 1,488 3,003  
U.K. Defined Benefit Plan [Member]          
Other comprehensive income:          
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement 3   58    
Pension and other postretirement benefits          
AOCI Attributable to Parent [Abstract]          
Balance at beginning of period (1,784) (32) (43) (32)  
Establishment of additional defined benefit plans         $ (1,752)
Separation-related adjustments (A) 0 0 50 0  
Other comprehensive income:          
Other Comprehensive Income (Loss), before Reclassifications, before Tax 4 1 (34) (1)  
Other Comprehensive Income (Loss) before Reclassifications, Tax (1) (1) 8 0  
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax 3 0 (26) (1)  
Amortization of net actuarial loss and prior service cost 36 1 153 3  
Tax expense (8) 0 (35) (1)  
Total amount reclassified from Accumulated other comprehensive loss, net of tax 28 1 118 2  
Total Other comprehensive income, net of tax 31 1 92 1  
Balance at end of period (1,753) (31) (1,753) (31)  
Foreign currency translation          
AOCI Attributable to Parent [Abstract]          
Balance at beginning of period (53) 296 338 282  
Separation-related adjustments (A) 0 0 396 0  
Other comprehensive income:          
Foreign currency translation 37 45 20 59  
Net amount reclassified to earnings from Accumulated other comprehensive income 0 0 22 0  
Total Other comprehensive income, net of tax 37 45 42 59  
Balance at end of period (16) 341 (16) 341  
Cash flow hedges          
AOCI Attributable to Parent [Abstract]          
Balance at beginning of period (11) 0 0 0  
Separation-related adjustments (A) 0 0 (4) 0  
Other comprehensive income:          
Other Comprehensive Income (Loss), before Reclassifications, before Tax 2 0 4 0  
Other Comprehensive Income (Loss) before Reclassifications, Tax (1) 0 (1) 0  
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax 1 0 3 0  
Amortization of net actuarial loss and prior service cost 14 0 3 0  
Tax expense (3) 0 (1) 0  
Total amount reclassified from Accumulated other comprehensive loss, net of tax 11 0 2 0  
Total Other comprehensive income, net of tax 12 0 5 0  
Balance at end of period 1 0 1 0  
Accumulated other comprehensive income (loss)          
AOCI Attributable to Parent [Abstract]          
Balance at beginning of period (1,848) 264 295 250  
Separation-related adjustments (A)     (450)    
Other comprehensive income:          
Total Other comprehensive income, net of tax 80 46 139 60  
Balance at end of period $ (1,768) $ 310 $ (1,768) $ 310