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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Pronghorn (Details) - Pronghorn [Member] - USD ($) $ in Millions	Jan. 01, 2017	Nov. 21, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent of ownership to sell		50.00%
Pronghorn [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds	$ 100