Income Taxes - Valuation Allowance (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance [Abstract]
State unused tax benefit carryforwards	$ 634	$ 651
Deferred capital loss on sale to affiliates	56	56
Total	$ 690	$ 707

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32537-109319

Name:	us-gaap_DeferredTaxAssetsValuationAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant