Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2013
Summary of Significant Accounting Policies [Line Items]
Accumulated other comprehensive loss revision for CTA				$ 97
Revision impact				151
SICAD 2 pre-tax charge	$ 58		$ 58
SIMADI pre-tax charge		$ 3
Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Marketable securities, maturity timing in months		3 months
Definite-lived intangible assets, useful life		1 year
Asset retirement obligations, useful life		1 year
Minimum [Member] | Equipment and Buildings [Member]
Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life		15 years
Minimum [Member] | Computer Software, Intangible Asset [Member]
Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life		5 years
Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Marketable securities, maturity timing in months		12 months
Definite-lived intangible assets, useful life		20 years
Asset retirement obligations, useful life		25 years
Maximum [Member] | Equipment and Buildings [Member]
Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life		25 years
Maximum [Member] | Computer Software, Intangible Asset [Member]
Summary of Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life		7 years
Pension Plan [Member]
Summary of Significant Accounting Policies [Line Items]
Accumulated other comprehensive loss revision for pension settlement charges				$ 54