Annual report pursuant to Section 13 and 15(d)

Income Taxes narrative (Details)

v3.19.3.a.u2
Income Taxes narrative (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2019
USD ($)
unit
Dec. 31, 2018
USD ($)
Operating Loss Carryforwards [Line Items]    
Increase (decrease) in valuation allowance $ (490) $ 686
Number Of Years In Cumulative Loss Position   3 years
Number Of Years In Cumulative Income Position 3 years  
Number of Long Term Agreements Commenced During The Year | unit 13  
Deferred Tax Assets, Valuation Allowance $ 196 $ 686
Deferred Tax Assets, Tax Credit Carryforwards 64 $ 28
Federal Tax [Member]    
Operating Loss Carryforwards [Line Items]    
Increase (decrease) in valuation allowance (493)  
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration 13,600  
Deferred Tax Assets, Tax Credit Carryforwards 61  
Federal Tax [Member] | Investment Tax Credit Carryforward [Member]    
Operating Loss Carryforwards [Line Items]    
Deferred Tax Assets, Tax Credit Carryforwards 52  
State Tax [Member]    
Operating Loss Carryforwards [Line Items]    
Increase (decrease) in valuation allowance (49)  
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration 3,100  
Deferred Tax Assets, Tax Credit Carryforwards 3  
State and Foreign Country [Member]    
Operating Loss Carryforwards [Line Items]    
Increase (decrease) in valuation allowance $ 52