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Hedges and Derivative Financial Instruments - Narrative (Details) - USD ($)
6 Months Ended 12 Months Ended
Jun. 30, 2019
Dec. 31, 2018
Derivative [Line Items]    
Net hedge ineffectiveness gain (loss) $ 0 $ 0
Derivatives accounted for as hedges | Interest rate derivatives    
Derivative [Line Items]    
Notional amount $ 700,000,000 $ 0