Long-Term Debt and Short-Term Borrowings (Details 1)			1 Months Ended				1 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended		12 Months Ended			1 Months Ended		1 Months Ended					1 Months Ended		1 Months Ended	12 Months Ended		12 Months Ended	1 Months Ended		3 Months Ended
	May 31, 2014 Medium-term notes program USD ($)	Sep. 30, 2011 Medium-term notes program USD ($)	Jul. 31, 2007 Eurobond 750 Million Euros Issued July 2007 EUR (€)	Dec. 31, 2013 Eurobond 750 Million Euros Issued July 2007 USD ($)	Aug. 31, 2010 Eurobond 750 Million Euros Issued July 2007 Interest rate swap contracts EUR (€)	Jul. 31, 2007 Eurobond 750 Million Euros Issued July 2007 Interest rate swap contracts EUR (€)	Dec. 31, 2007 Eurobond 275 Million Euros Issued December 2007 EUR (€)	Dec. 31, 2013 Eurobond 275 Million Euros Issued December 2007 USD ($)	Nov. 30, 2013 Eurobond 600 Million Euros Issued November 2013 EUR (€)	Dec. 31, 2014 Eurobond 600 Million Euros Issued November 2013 USD ($)	Sep. 30, 2011 Fixed rate Medium term note due 2016	Dec. 31, 2014 Fixed rate Medium term note due 2016 USD ($)	Jun. 30, 2012 Fixed rate medium term note due 2017	Dec. 31, 2014 Fixed rate medium term note due 2017 USD ($)	Jun. 30, 2014 Fixed rate medium term note due 2019 USD ($)	Dec. 31, 2014 Fixed rate medium term note due 2019 USD ($)	Nov. 30, 2014 Floating rate Euro Medium term note due 2018	Dec. 31, 2014 Floating rate Euro Medium term note due 2018 EUR (€)	Nov. 30, 2014 Fixed rate Euro Medium term note due 2026	Dec. 31, 2014 Fixed rate Euro Medium term note due 2026 EUR (€)	Jun. 30, 2012 Fixed rate medium term note due 2022	Dec. 31, 2014 Fixed rate medium term note due 2022 USD ($)	Jun. 30, 2014 Fixed rate medium term note due 2044	Dec. 31, 2014 Fixed rate medium term note due 2044 USD ($)	Dec. 31, 2014 Floating rate notes due in 2027, 2040 and 2041	Dec. 31, 2014 Floating rate notes due in 2027, 2040 and 2041 Maximum	Dec. 31, 2014 Floating rate notes due in 2027, 2040 and 2041 Minimum	Mar. 31, 2007 Fixed rate 30-year bond due 2037	Dec. 31, 2014 Fixed rate 30-year bond due 2037 USD ($)	Dec. 31, 1998 Fixed rate 30-year debenture due 2028	Dec. 31, 2014 Fixed rate 30-year debenture due 2028 USD ($)	Dec. 31, 2014 Eurobond notes which matured in 2014 EUR (€)	Dec. 31, 2014 Fixed rate Eurobond Due 2021 EUR (€)	Dec. 31, 2014 Floating rate Eurobond Due 2021 EUR (€)	Dec. 31, 2004 Floating rate note due 2044 USD ($)	Dec. 31, 2014 Floating rate note due 2044 USD ($)	Aug. 31, 2014 Five-year credit facility agreement USD ($)	Dec. 31, 2014 Five-year credit facility agreement USD ($)	Dec. 31, 2014 Stand alone letters of credit USD ($)	Dec. 31, 2014 Bank guarantees issued and outstanding USD ($)	Dec. 31, 2012 Three-year credit facility agreement with JP Morgan Chase Bank USD ($)	Dec. 31, 2012 Three-year credit facility agreement with JP Morgan Chase Bank GBP (£)	Dec. 31, 2014 Three-year credit facility agreement with JP Morgan Chase Bank GBP (£)	Mar. 31, 2014 Three-year credit facility agreement with JP Morgan Chase Bank GBP (£)
Long-Term Debt
Term of debt instrument			7 years				7 years		8 years		5 years		5 years		5 years		4 years		12 years		10 years		30 years					30 years		30 years					40 years
Medium-term notes program established in connection with a "well-known seasoned issuer" shelf registration	$ 9,000,000,000	$ 3,000,000,000
Principal amount			750,000,000	1,042,000,000			275,000,000	382,000,000	600,000,000	753,000,000		1,000,000,000		650,000,000	625,000,000	600,000,000		500,000,000		750,000,000		600,000,000		325,000,000					750,000,000		330,000,000	1,025,000,000	300,000,000	300,000,000	60,000,000	55,000,000
Amount of notes under medium term note program that were previously issued	2,250,000,000
Interest rate, stated percentage (as a percent)			5.00%				5.00%		1.875%		1.375%		1.00%		1.625%				1.50%		2.00%		3.875%					5.70%		6.01%
Repurchase price of floating rate notes (as a percent)																										100.00%	99.00%									100.00%
Derivative notional amount						400,000,000			300,000,000						600,000,000
Termination of notional amount of fixed-to-floating interest rate swap					150,000,000
Notional amount remaining after partial termination of fixed-to-floating interest rate swap					250,000,000
Number of years after date of issuance that put options commence																									10 years
Number of years after put options commence when additional put options occur on each anniversary thereafter until final maturity																									3 years
Line of Credit Facility
Term of credit facility																																					5 years				3 years	3 years
Credit facility amount prior to new agreement																																					1,500,000,000
Current borrowing capacity																																						2,250,000,000			106,000,000	66,000,000
Maximum increase available subject to lender approval																																						2,250,000,000
Maximum borrowing capacity including portion subject to lender approval																																						4,500,000,000
Amount of letters of credit outstanding utilized in connection with normal business activities																																							219,000,000
Repayment of Lines of Credit																																								$ 18,000,000			£ 30,000,000	£ 36,000,000
Required minimum EBITDA to Interest Ratio																																						3
Actual EBITDA to Interest Ratio																																						60
Number of consecutive quarters over which the ratio of required EBITDA to Interest Ratio is calculated																																						4