Description of risks that arise due to the volume of business transacted with a particular customer. At a minimum, the description informs financial statement users of the general nature of the risk, but excludes "Information about Major Customers" that may be disclosed elsewhere (for instance, segment disclosures).

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Summary of Significant Accounting Policies Major Customers and Credit Risk (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended	12 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration Risk [Line Items]
Concentration percentage						100.00%	100.00%	100.00%
Receivable with Imputed Interest, Face Amount		$ 65		$ 120	$ 120
Trade Receivables Held-for-sale, Reconciliation to Cash Flow, Deductions from Held-for-sale		$ 65		120
Receivable With Imputed Interest, Term		3 years			3 years
Receivable with Imputed Interest, Effective Yield (Interest Rate)		4.625%			6.50%
Financing Receivable, Allowance for Credit Losses, Write-downs				$ 84			$ 76
Proceeds from Sale of Notes Receivable	$ 59		$ 44
Gain (Loss) on Sale of Notes Receivable			$ 8
Concentration Risk, Customer						no	0	0
Accounts Receivable [Member] \| Eastern Hemisphere [Member] \| Geographic Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration percentage						57.00%
Accounts Receivable [Member] \| Western Hemisphere [Member] \| Geographic Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration percentage						43.00%
Accounts Receivable [Member] \| UNITED STATES \| Geographic Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration percentage						19.00%
Accounts Receivable [Member] \| KUWAIT \| Geographic Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration percentage						10.00%
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration percentage						10.00%	10.00%	10.00%