Employee Benefit Plans - One-Percentage-Point Change in Assumed Health Care Cost (Details) $ in Millions	12 Months Ended
Dec. 31, 2015 USD ($)
Compensation and Retirement Disclosure [Abstract]
1% Health care cost trend rate increase	$ 13
1% Health care cost trend rate decrease	$ (11)

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration