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

Goodwill and Other Intangible Assets (Details Textual) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended
	Oct. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Goodwill [Line Items]
Goodwill		$ 9,884	$ 9,453	$ 107,823	$ 186,844
Fair value in excess of carrying value		1.00%
Goodwill impairment tests, period of estimates of cash flow, maximum, years	18
Assumed terminal growth rate	3.00%
Goodwill, amortization period, years		15 years
Finite-lived intangible assets		7,585
Natural Gas Liquids Energy And Its General Partner [Member]
Goodwill [Line Items]
Goodwill		65,400
White Cliffs Pipeline, LLC [Member]
Goodwill [Line Items]
Goodwill		8,700
SemMexico [Member]
Goodwill [Line Items]
Goodwill		9,884	9,453
Weighted average cost of capital	12.20%
Customer Relationships [Member] \| SemMexico [Member]
Goodwill [Line Items]
Finite-lived intangible assets		5,000
Unpatented Technology [Member] \| SemMexico [Member]
Goodwill [Line Items]
Finite-lived intangible assets		$ 2,200