Carrying Amount of Goodwill by Segment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended			12 Months Ended	3 Months Ended	12 Months Ended
Dec. 31, 2011	Dec. 31, 2011 Pipelines & Terminals	Dec. 31, 2010 Pipelines & Terminals	Dec. 31, 2011 International Operations	Sep. 30, 2011 Natural Gas Storage	Dec. 31, 2011 Natural Gas Storage	Dec. 31, 2011 Energy Services	Dec. 31, 2010 Energy Services	Dec. 31, 2011 Development & Logistics	Dec. 31, 2010 Development & Logistics
Goodwill [Line Items]
Beginning balance	$ 432,124	$ 248,250	$ 248,250			$ 169,560	$ 1,132	$ 1,132	$ 13,182	$ 13,182
Acquisition	490,536			490,536
Impairment charge	(169,560)				(169,600)	(169,560)
Ending Balance	$ 753,100	$ 248,250	$ 248,250	$ 490,536			$ 1,132	$ 1,132	$ 13,182	$ 13,182

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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+ Details

- Definition

The aggregate amount of goodwill acquired in the period and allocated to the reportable segment. The value is stated at fair value based on the purchase price allocation.

+ References+ Details

- Definition

Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

+ References

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+ Details