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Accounts Receivable, Net (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Receivables [Abstract]    
Allowance for bill adjustments and uncollectible accounts $ 56bni_AllowanceForBillAdjustmentsAndDoubtfulAccountsReceivableCurrent $ 56bni_AllowanceForBillAdjustmentsAndDoubtfulAccountsReceivableCurrent
Accounts receivable greater than 90 days old $ 50bni_AccountsReceivableCurrentGreaterThan90DaysPastDue $ 35bni_AccountsReceivableCurrentGreaterThan90DaysPastDue