XML 53 R35.htm IDEA: XBRL DOCUMENT v3.8.0.1
Revenues - Additional Information (Details)
$ in Millions
3 Months Ended
Mar. 31, 2018
USD ($)
segment
Dec. 31, 2017
USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]    
Operating segments number | segment 3  
Minimum Volume Commitments    
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]    
Counterparty deficiencies $ 59 $ 57
Deferred revenue 44 37
Counterparty deficiencies unbilled and uncollected $ 15 $ 20