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Revenue Recognition - Performance Obligation (Details)
$ in Millions
Mar. 31, 2019
USD ($)
Revenue from Contract with Customer [Abstract]  
Revenue to be recognized in future periods $ 500
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01  
Revenue from Contract with Customer [Abstract]  
Revenue to be recognized in future periods $ 350
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]  
Revenue to be recognized in future periods, expected timing of satisfaction, period 1 year