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

Goodwill (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 31, 2012	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill [Line Items]
Goodwill			$ 1,468	$ 1,696
Impairment Charge		252	252	0	0
Acquisition	24		24
Natural Gas Distribution [Member]
Goodwill [Line Items]
Goodwill			746	746
Impairment Charge			0
Acquisition			0
Interstate Pipelines [Member]
Goodwill [Line Items]
Goodwill			579	579
Impairment Charge			0
Acquisition			0
Competitive Natural Gas Sales and Services [Member]
Goodwill [Line Items]
Goodwill			83	335
Impairment Charge			252
Acquisition			0
Field Services [Member]
Goodwill [Line Items]
Goodwill			49	25
Impairment Charge			0
Acquisition			24
Other Operations [Member]
Goodwill [Line Items]
Goodwill			11	11
Impairment Charge			0
Acquisition			$ 0