Risk Management Amounts reclassified out of other comprehensive income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	$ (14)	$ 19	$ 24	$ 66
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	(82)	89	(4)	132
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	11	(29)	13	(30)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(85)	79	33	168
Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Net Of Tax Portion Attributable To Parent	(56)	(40)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent	(38)	(47)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent	(78)	(43)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Reclassification Adjustments, Net of Tax	(2)	1
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax	(2)	1
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	18	(7)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	0	0
Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretiremen tBenefit Plans Net Of Tax Portion Attributable To Parent	0	0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(118)	(89)
OCI before Reclassifications [Member]
Derivatives, Fair Value [Line Items]
Other comprehensive income (loss) before reclassifications, net of tax, portion attributable to parent	(136)	(82)
Amounts reclassified from AOCI [Member]
Derivatives, Fair Value [Line Items]
Other comprehensive income reclassified from accumulated other comprehensive income, net of tax, portion attributable to parent	$ 18	$ (7)