v3.19.3.a.u2
Derivative and Financial Instruments - FX Notional (Details)
 12 Months Ended
Dec. 31, 2019
USD ($)
Dec. 31, 2019
CAD ($)
Dec. 31, 2019
GBP (£)
Dec. 31, 2018
USD ($)
Dec. 31, 2018
CAD ($)
Dec. 31, 2018
GBP (£)
Trading Activity, Gains and Losses, Net [Line Items]            
Description of Foreign Currency Derivative Instruments Not Designated as Hedging Instruments Activities In December 2017, we entered into foreign exchange zero cost collars buying the right to sell $1.25 billion CAD at $0.707 CAD and selling the right to buy $1.25 billion CAD at $0.842 CAD against the U.S. dollar. The collar expired during the second quarter of 2019 and we entered into new foreign currency exchange forward contracts to sell $1.35 billion CAD at $0.748 CAD against the U.S. dollar.          
Sell U.S. dollar, buy British pound. | Not Designated as Hedging Instrument [Member]            
Trading Activity, Gains and Losses, Net [Line Items]            
Net notional position of foreign currency exchange derivatives | $ $ 0     $ 805,000,000    
Buy British Pound Sell Euro [Member] | Not Designated as Hedging Instrument [Member]            
Trading Activity, Gains and Losses, Net [Line Items]            
Net notional position of foreign currency exchange derivatives | £     £ 4,000,000     £ 0
Sell British pound, buy other currencies [Member] | Not Designated as Hedging Instrument [Member]            
Trading Activity, Gains and Losses, Net [Line Items]            
Net notional position of foreign currency exchange derivatives | £ [1]     £ 0     £ 21,000,000
Sell Canadian dollar, buy U.S. dollar [Member] | Not Designated as Hedging Instrument [Member]            
Trading Activity, Gains and Losses, Net [Line Items]            
Net notional position of foreign currency exchange derivatives | $   $ 1,337,000,000     $ 1,242,000,000  
[1] <div>*Primarily euro and Norwegian krone.</div>