Long-Term Debt and Credit Facilities (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Line of credit facility [Line Items]
Unused borrowing capacity	$ 3,001
Amended Domestic Revolving Credit Facility 2370 Million Capacity [Member]
Line of credit facility [Line Items]
Maximum borrowing capacity	2,370
Line of Credit Facility, Expiration Date	Nov. 30, 2019
Debt Instrument, Term	5 years
Domestic Revolving Credit Facility 165 Million Capacity [Member]
Line of credit facility [Line Items]
Maximum borrowing capacity	165
Line of Credit Facility, Expiration Date	Nov. 30, 2015
Domestic Revolving Credit Facility 20 Million Capacity [Member]
Line of credit facility [Line Items]
Maximum borrowing capacity	20
Line of Credit Facility, Expiration Date	Dec. 31, 2015
Domestic Revolving Credit Facility 1850 Million Capacity [Member]
Line of credit facility [Line Items]
Maximum borrowing capacity		$ 1,850
Line of Credit Facility, Expiration Date		Nov. 30, 2018
Debt Instrument, Term		5 years