Asset Retirement Obligations (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Asset Retirement Obligations [Abstract]
Carrying Amount at Beginning of Period	$ 665,944		$ 587,084
Liabilities Incurred	103,284		107,378
Liabilities Settled	(70,510)	[1]	(77,384)	[1]
Accretion	35,180		30,020
Revisions	38,552		15,287
Foreign Currency Translations	(10,552)		3,559
Carrying Amount at End of Period	761,898		665,944
Current Portion	43,857		30,127
Noncurrent Portion	$ 718,041		$ 635,817

[1] Includes settlements related to asset sales.