Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Operating Loss Carryforwards [Line Items]
Income tax expense	$ 9	$ 87	$ 105	$ 183
Effective tax rate	19.00%	67.00%	23.00%	49.00%
Federal statutory income tax rate	35.00%	35.00%	35.00%	35.00%
Increase in operating loss carryforward			913
Deferred tax assets, operating loss carryforwards	932		932
Increase in alternative minimum, general business, and foreign tax credits			292
Deferred tax assets, alternative minimum, general business, and foreign tax credits	296		296
Valuation allowance, change in amount			98
Unrecognized tax benefits, increases resulting from acquisition			313
Unrecognized tax benefits	375		375
NGPL [Member]
Operating Loss Carryforwards [Line Items]
Ownership interest	20.00%		20.00%
Florida Gas Pipeline [Member]
Operating Loss Carryforwards [Line Items]
Ownership interest	50.00%		50.00%
Equity Method Investee [Member]
Operating Loss Carryforwards [Line Items]
Loss eontingency, estimate of possible loss		$ 90		$ 90