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Summary of Significant Accounting Policies (Tables)
12 Months Ended
Dec. 31, 2019
Accounting Policies [Abstract]  
Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]  
Research and Development
($ in millions)
2019

 
2018

 
2017

Research and development – total

$456

 

$464

 

$472

Less depreciation on research facilities
24

 
23

 
21

Research and development, net

$432

 

$441

 

$451