Derivative and Hedging Activities - Narrative (Details)			3 Months Ended													1 Months Ended
	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2015 Interest Rate Contract [Member] USD ($)	Dec. 31, 2014 Interest Rate Contract [Member] USD ($)	Mar. 31, 2015 Multi-Counterparty Hedging Facility [Member] USD ($) counterparty	Mar. 31, 2015 Multi-Counterparty Hedging Facility [Member] Minimum [Member]	Mar. 31, 2015 Multi-Counterparty Hedging Facility [Member] Credit Risk [Member] counterparty	Mar. 31, 2015 Multi-Counterparty Hedging Facility [Member] Energy Related Derivative [Member] MMBoe	Mar. 31, 2015 Multi-Counterparty Hedging Facility [Member] Price Risk Derivative [Member] MMBoe	Mar. 31, 2015 Multi-Counterparty Hedging Facility [Member] Basis Derivative [Member] MMBoe	May 05, 2015 Multi-Counterparty Hedging Facility [Member] Subsequent Event [Member] USD ($)	Mar. 31, 2015 Senior Notes [Member] Minimum [Member] USD ($)	Mar. 31, 2015 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] USD ($)	Dec. 31, 2014 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 ($)	Dec. 31, 2006 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] Cross Currency Interest Rate Contract [Member] EUR (€)	Mar. 31, 2015 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] Cross Currency Interest Rate Contract [Member] USD ($)	Mar. 31, 2015 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] Cross Currency Interest Rate Contract [Member] EUR (€)	Dec. 31, 2014 6.25% Euro-Denominated Senior Notes Due 2017 [ Member] Senior Notes [Member] Cross Currency Interest Rate Contract [Member] USD ($)	Mar. 31, 2015 Cash Flow Hedging [Member] USD ($)	Dec. 31, 2014 Cash Flow Hedging [Member] USD ($)	Mar. 31, 2014 Cash Flow Hedging [Member] USD ($)	Dec. 31, 2013 Cash Flow Hedging [Member] USD ($)	Mar. 31, 2015 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Cash Flow Hedging [Member] USD ($)	Mar. 31, 2015 Not Designated as Hedging Instrument [Member] Interest Rate Contract [Member] USD ($)	Dec. 31, 2014 Not Designated as Hedging Instrument [Member] Interest Rate Contract [Member] USD ($)	Mar. 31, 2015 Designated as Hedging Instrument [Member] Foreign Exchange Contract [Member] USD ($)	Dec. 31, 2014 Designated as Hedging Instrument [Member] Foreign Exchange Contract [Member] USD ($)
Derivative [Line Items]
Derivative, Amount of Hedged Item			$ 400,000,000	$ 850,000,000
Derivative Assets (Liabilities), at Fair Value, Net	395,000,000	652,000,000																								(3,000,000)	(17,000,000)	(103,000,000)	(53,000,000)
Amortization Period of Deferred Gain (Loss) on Discontinuation of Fair Value Hedge			6 years
Deferred (Gain) Loss on Discontinuation of Fair Value Hedge			9,000,000
Euro-denominated debt in notes payable, adjusted value			9,000,000	10,000,000								50,000,000	369,000,000	416,000,000	344,000,000			369,000,000
Derivative, Forward Exchange Rate																1.3325		1.0731		1.2098
Semi Annual Interest Rate Swap Payments By Counterparty																	11,000,000		344,000,000
Dollar Equivalent Interest Rate																7.491%	7.491%
Short-term Debt, Refinanced, Description																17,000,000		459,000,000
Derivative Liability, Fair Value, Gross Liability																										(3,000,000)	(17,000,000)	(103,000,000)	(53,000,000)
Accumulated other comprehensive loss	(134,000,000)	(143,000,000)																			(134,000,000)	(143,000,000)	(153,000,000)	(167,000,000)	(126,000,000)
Expected amount to be transferred of during the next 12 months	19,000,000
Number of counterparties in hedge facility					17		16
Multi-counterparty hedging facility, committed to provide a trading capacity (in tcfe)								1,031,000,000
Borrowing capacity					$ 16,500,000,000						$ 10,000,000,000
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
Multi-counterparty hedge facility, hedged total (in tcfe)									128,000,000	9,000,000