Accounts Receivable - Accounts Receivable (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 751
Less: allowance for doubtful accounts	(3)
Accounts receivable, less allowance	748
Trade and purchased receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	562
Earned and unbilled receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	165
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 24
Predecessor
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable		$ 741
Less: allowance for doubtful accounts		(29)
Accounts receivable, less allowance		712
Predecessor | Trade and purchased receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable		588
Predecessor | Earned and unbilled receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable		140
Predecessor | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable		$ 13