Debt, Capitalized Interest (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Capitalized Interest (Textual)
Interest costs incurred, capitalized	$ 20	$ 16

Amount of interest capitalized, including amount of allowance for funds used during construction.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Allowance for Funds Used during Construction
-URI http://asc.fasb.org/extlink&oid=6504829

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 835
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433

Name:	us-gaap_InterestCostsIncurredCapitalized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration