Estimates, Significant Accounting Policies and Balance Sheet Detials (Assets and liabilities measured and recorded at fair value on a recurring basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Long-term Debt	$ 19,340	$ 17,088
Fair Value, Measurements, Recurring [Member]
Interest rate derivatives, Assets	3	47
Price Risk Derivative Assets, at Fair Value	661	227
Assets, Fair Value Disclosure	664	274
Interest rate derivatives, Liabilities	(155)	(95)
Price Risk Derivative Liabilities, at Fair Value	(578)	(223)
Liabilities, Fair Value Disclosure, Recurring	733	318
Basis Swaps IFERC NYMEX (MMBtu) [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Liabilities, Fair Value Disclosure		1
Forward Swaps [Member] | Commodity Derivatives - NGLs [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	46	5
Price Risk Derivative Liabilities, at Fair Value	(32)	(5)
Forward Swaps [Member] | Commodity Derivatives - Refined Products [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value		5
Price Risk Derivative Liabilities, at Fair Value	(7)	(5)
Forward Swaps [Member] | Commodity Derivatives - Power [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	3	3
Price Risk Derivative Liabilities, at Fair Value	(4)	(1)
Power - Option - Calls [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Securities	4
Forward Physical Swaps [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Securities	1
Basis Swaps IFERC/NYMEX [Member] | Commodity Derivatives - Natural Gas [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	19	5
Price Risk Derivative Liabilities, at Fair Value	(18)	(4)
Swing Swaps IFERC [Member] | Commodity Derivatives - Natural Gas [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	26	8
Price Risk Derivative Liabilities, at Fair Value	(25)	(6)
Fixed Swaps Futures [Member] | Commodity Derivatives - Natural Gas [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	541	201
Price Risk Derivative Liabilities, at Fair Value	(490)	(201)
Fixed Swaps Futures [Member] | Commodity Derivatives - Refined Products [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	21
Power - Futures [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Liabilities, Fair Value Disclosure	(2)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Interest rate derivatives, Assets	0	0
Price Risk Derivative Assets, at Fair Value	632	217
Assets, Fair Value Disclosure	632	217
Interest rate derivatives, Liabilities	0	0
Price Risk Derivative Liabilities, at Fair Value	(551)	(215)
Liabilities, Fair Value Disclosure, Recurring	551	215
Fair Value, Inputs, Level 1 [Member] | Basis Swaps IFERC NYMEX (MMBtu) [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Liabilities, Fair Value Disclosure		0
Fair Value, Inputs, Level 1 [Member] | Forward Swaps [Member] | Commodity Derivatives - NGLs [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	46	5
Price Risk Derivative Liabilities, at Fair Value	(32)	(5)
Fair Value, Inputs, Level 1 [Member] | Forward Swaps [Member] | Commodity Derivatives - Refined Products [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value		5
Price Risk Derivative Liabilities, at Fair Value	(7)	(5)
Fair Value, Inputs, Level 1 [Member] | Forward Swaps [Member] | Commodity Derivatives - Power [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	0	0
Fair Value, Inputs, Level 1 [Member] | Power - Option - Calls [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Securities	4
Fair Value, Inputs, Level 1 [Member] | Forward Physical Swaps [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Securities	0
Fair Value, Inputs, Level 1 [Member] | Basis Swaps IFERC/NYMEX [Member] | Commodity Derivatives - Natural Gas [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	19	5
Price Risk Derivative Liabilities, at Fair Value	(18)	(4)
Fair Value, Inputs, Level 1 [Member] | Swing Swaps IFERC [Member] | Commodity Derivatives - Natural Gas [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	1	1
Price Risk Derivative Liabilities, at Fair Value	(2)	0
Fair Value, Inputs, Level 1 [Member] | Fixed Swaps Futures [Member] | Commodity Derivatives - Natural Gas [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	541	201
Price Risk Derivative Liabilities, at Fair Value	(490)	(201)
Fair Value, Inputs, Level 1 [Member] | Fixed Swaps Futures [Member] | Commodity Derivatives - Refined Products [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	21
Fair Value, Inputs, Level 1 [Member] | Power - Futures [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Liabilities, Fair Value Disclosure	(2)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Interest rate derivatives, Assets	3	47
Price Risk Derivative Assets, at Fair Value	29	10
Assets, Fair Value Disclosure	32	57
Interest rate derivatives, Liabilities	(155)	(95)
Price Risk Derivative Liabilities, at Fair Value	(27)	(8)
Liabilities, Fair Value Disclosure, Recurring	182	103
Fair Value, Inputs, Level 2 [Member] | Basis Swaps IFERC NYMEX (MMBtu) [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Liabilities, Fair Value Disclosure		(1)
Fair Value, Inputs, Level 2 [Member] | Forward Swaps [Member] | Commodity Derivatives - NGLs [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	0	0
Fair Value, Inputs, Level 2 [Member] | Forward Swaps [Member] | Commodity Derivatives - Refined Products [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value		0
Price Risk Derivative Liabilities, at Fair Value	0	0
Fair Value, Inputs, Level 2 [Member] | Forward Swaps [Member] | Commodity Derivatives - Power [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	3	3
Price Risk Derivative Liabilities, at Fair Value	(4)	(1)
Fair Value, Inputs, Level 2 [Member] | Power - Option - Calls [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Securities	0
Fair Value, Inputs, Level 2 [Member] | Forward Physical Swaps [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Securities	1
Fair Value, Inputs, Level 2 [Member] | Basis Swaps IFERC/NYMEX [Member] | Commodity Derivatives - Natural Gas [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	0	0
Fair Value, Inputs, Level 2 [Member] | Swing Swaps IFERC [Member] | Commodity Derivatives - Natural Gas [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	25	7
Price Risk Derivative Liabilities, at Fair Value	(23)	(6)
Fair Value, Inputs, Level 2 [Member] | Fixed Swaps Futures [Member] | Commodity Derivatives - Natural Gas [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	0	0
Price Risk Derivative Liabilities, at Fair Value	0	0
Fair Value, Inputs, Level 2 [Member] | Fixed Swaps Futures [Member] | Commodity Derivatives - Refined Products [Member] | Fair Value, Measurements, Recurring [Member]
Price Risk Derivative Assets, at Fair Value	0
Fair Value, Inputs, Level 2 [Member] | Power - Futures [Member] | Commodity [Member] | Fair Value, Measurements, Recurring [Member]
Trading Liabilities, Fair Value Disclosure	$ 0