Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2011

Asset Retirement Obligations [Abstract]

Company Before Tax Asset Retirement Obligation

	2011			2010			2009
Balance at January 1	$	12,488		$	10,175		$	9,395
Liabilities incurred		62			129			144
Liabilities settled		(1,316	)		(755	)		(757	)
Accretion expense		628			513			463
Revisions in estimated cash flows		905			2,426			930
Balance at December 31	$	12,767		$	12,488		$	10,175