Asset Retirement Obligations 1 (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Platforms And Lines [Member]
ARO [Line Items]
ARO Underlying Asset	$ 3,180
Other ARO Asset [Member]
ARO [Line Items]
ARO Underlying Asset	4,941
Natural Gas Storage Wells [Member]
ARO [Line Items]
ARO Underlying Asset	$ 517