Impairment of long-lived assets

6 Months Ended

Jun. 30, 2013

Impaired Long-Lived Assets Held and Used [Line Items]

Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]

Impairment of long-lived assets

During the second quarters of 2013 and 2012, the Company recognized impairments of coalbed natural gas gathering assets at the pipeline and energy services segment of $14.5 million ($9.0 million after tax) and $2.7 million ($1.7 million after tax), respectively, which are recorded in operation and maintenance expense on the Consolidated Statements of Income. The impairments are related to coalbed natural gas gathering assets located in Wyoming and Montana where there has been a significant decline in natural gas development and production activity largely due to low natural gas prices. The coalbed natural gas gathering assets were written down to fair value that was determined using the income approach. For more information on this nonrecurring fair value measurement see Note 14.