Derivative and Hedging Activities - Narrative (Details)	9 Months Ended														1 Months Ended
	Sep. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2014 Senior Notes [Member] USD ($)	Apr. 24, 2014 Senior Notes [Member] USD ($)	Sep. 30, 2014 Multi-Counterparty Hedging Facility [Member] USD ($) counterparty	Sep. 30, 2014 Multi-Counterparty Hedging Facility [Member] Credit Risk [Member] counterparty	Sep. 30, 2014 Multi-Counterparty Hedging Facility [Member] Energy Related Derivative [Member] MMBoe	Sep. 30, 2014 Swap [Member] USD ($)	Dec. 31, 2013 Swap [Member] USD ($)	Sep. 30, 2014 Basis Derivative [Member] Multi-Counterparty Hedging Facility [Member] MMBoe	Sep. 30, 2014 Price Risk Derivative [Member] Multi-Counterparty Hedging Facility [Member] MMBoe	Sep. 30, 2014 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] USD ($)	Dec. 31, 2013 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] USD ($)	Dec. 31, 2006 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] USD ($)	Dec. 31, 2006 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] Cross Currency Interest Rate Contract [Member] USD ($)	Dec. 31, 2006 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] Cross Currency Interest Rate Contract [Member] EUR (€)	Sep. 30, 2014 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] Cross Currency Interest Rate Contract [Member] USD ($)	Sep. 30, 2014 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] Cross Currency Interest Rate Contract [Member] EUR (€)	Dec. 31, 2013 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] Cross Currency Interest Rate Contract [Member] USD ($)	Sep. 30, 2014 Minimum [Member] Senior Notes [Member] USD ($)	Sep. 30, 2014 Minimum [Member] Multi-Counterparty Hedging Facility [Member]	Sep. 30, 2014 Accumulated Other Comprehensive Income (Loss) [Member] USD ($)	Dec. 31, 2013 Accumulated Other Comprehensive Income (Loss) [Member] USD ($)	Sep. 30, 2013 Accumulated Other Comprehensive Income (Loss) [Member] USD ($)	Dec. 31, 2012 Accumulated Other Comprehensive Income (Loss) [Member] USD ($)	Sep. 30, 2014 Accumulated Other Comprehensive Income (Loss) [Member] Cash Flow Hedging [Member] USD ($)	Jun. 30, 2014 Accumulated Other Comprehensive Income (Loss) [Member] Cash Flow Hedging [Member] USD ($)	Dec. 31, 2013 Accumulated Other Comprehensive Income (Loss) [Member] Cash Flow Hedging [Member] USD ($)	Sep. 30, 2013 Accumulated Other Comprehensive Income (Loss) [Member] Cash Flow Hedging [Member] USD ($)	Jun. 30, 2013 Accumulated Other Comprehensive Income (Loss) [Member] Cash Flow Hedging [Member] USD ($)	Dec. 31, 2012 Accumulated Other Comprehensive Income (Loss) [Member] Cash Flow Hedging [Member] USD ($)
Derivative [Line Items]
Interest Rate Derivatives, at Fair Value, Net								$ 52,000,000	$ 98,000,000
Terminated Qualifying Interest Rate Derivative Transactions Duration	6 years
Derivative, Amount of Hedged Item								1,450,000,000	2,250,000,000
Number of counterparties in hedge facility					17	18
Multi-counterparty hedging facility, committed to provide a trading capacity (in tcfe)							1,031,000,000
Multi-counterparty hedge facility, committed to provide an aggregate mark-to-market capacity					16,500,000,000
Multi-counterparty hedge facility, hedged total (in tcfe)										16,000,000	178,000,000
Natural gas and oil proved reserves, the value of which must cover the fair value of the transactions outstanding under the facility, multiplier					1.30																1.65
Deferred (Gain) Loss on Discontinuation of Fair Value Hedge	10,000,000
Derivative, Forward Exchange Rate															1.3325		1.2631		1.3743
Semi Annual Interest Rate Swap Payments By Counterparty																11,000,000		344,000,000
Short-term Debt, Refinanced, Description															17,000,000		459,000,000
Dollar Equivalent Interest Rate															7.491%	7.491%
Derivative liability, gross liability																	30,000,000
Derivative Asset, Fair Value, Gross Asset																			2,000,000
Euro-denominated debt in notes payable, adjusted value	1,500,000,000		3,000,000,000	3,000,000,000								435,000,000	473,000,000	344,000,000			435,000,000			50,000,000
Derivative Instruments, Gain (Loss) Reclassification from AOCI to Income, Estimated Net Amount to be Transferred	(147,000,000)
Accumulated other comprehensive loss	(151,000,000)	(162,000,000)																				(151,000,000)	(162,000,000)	(169,000,000)	(182,000,000)	(151,000,000)	(154,000,000)	(167,000,000)	(174,000,000)	(178,000,000)	(189,000,000)
Expected amount to be transferred of during the next 12 months	$ 26,000,000