Fair Value Measurements Fair Value Heigharchy (Details) - USD ($) $ in Millions | Sep. 30, 2016 | Dec. 31, 2015 |
Derivative Liability, Fair Value, Gross Liability | $ (565) | $ (526) |
Fair Value, Measurements, Recurring [Member] | | |
Interest rate derivatives, Assets | 18 | |
Price Risk Derivative Assets, at Fair Value | 141 | 448 |
Assets, Fair Value Disclosure, Recurring | 159 | 448 |
Interest rate derivatives, Liabilities | (375) | (171) |
Embedded Derivative, Fair Value of Embedded Derivative Liability | (1) | (5) |
Price Risk Derivative Liabilities, at Fair Value | (189) | (350) |
Liabilities, Fair Value Disclosure, Recurring | (565) | (526) |
Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Interest rate derivatives, Assets | 0 | |
Price Risk Derivative Assets, at Fair Value | 130 | 414 |
Assets, Fair Value Disclosure, Recurring | 130 | 414 |
Interest rate derivatives, Liabilities | 0 | 0 |
Embedded Derivative, Fair Value of Embedded Derivative Liability | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | (181) | (318) |
Liabilities, Fair Value Disclosure, Recurring | (181) | (318) |
Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Interest rate derivatives, Assets | 18 | |
Price Risk Derivative Assets, at Fair Value | 11 | 34 |
Assets, Fair Value Disclosure, Recurring | 29 | 34 |
Interest rate derivatives, Liabilities | (375) | (171) |
Embedded Derivative, Fair Value of Embedded Derivative Liability | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | (8) | (32) |
Liabilities, Fair Value Disclosure, Recurring | (383) | (203) |
Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Interest rate derivatives, Assets | 0 | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Interest rate derivatives, Liabilities | 0 | 0 |
Embedded Derivative, Fair Value of Embedded Derivative Liability | | (5) |
Derivative Liability, Fair Value, Gross Liability | (1) | |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Liabilities, Fair Value Disclosure, Recurring | (1) | (5) |
Commodity Derivatives - Natural Gas [Member] | Basis Swaps IFERC/NYMEX [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | 5 | 16 |
Price Risk Derivative Liabilities, at Fair Value | (5) | (16) |
Commodity Derivatives - Natural Gas [Member] | Basis Swaps IFERC/NYMEX [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | 5 | 16 |
Price Risk Derivative Liabilities, at Fair Value | (5) | (16) |
Commodity Derivatives - Natural Gas [Member] | Basis Swaps IFERC/NYMEX [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Commodity Derivatives - Natural Gas [Member] | Basis Swaps IFERC/NYMEX [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Commodity Derivatives - Natural Gas [Member] | Swing Swaps IFERC [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | 3 | 10 |
Price Risk Derivative Liabilities, at Fair Value | (3) | (12) |
Commodity Derivatives - Natural Gas [Member] | Swing Swaps IFERC [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 2 |
Price Risk Derivative Liabilities, at Fair Value | 0 | (2) |
Commodity Derivatives - Natural Gas [Member] | Swing Swaps IFERC [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | 3 | 8 |
Price Risk Derivative Liabilities, at Fair Value | (3) | (10) |
Commodity Derivatives - Natural Gas [Member] | Swing Swaps IFERC [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Commodity Derivatives - Natural Gas [Member] | Fixed Swaps/Futures [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | 24 | 274 |
Price Risk Derivative Liabilities, at Fair Value | (36) | (203) |
Commodity Derivatives - Natural Gas [Member] | Fixed Swaps/Futures [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | 24 | 274 |
Price Risk Derivative Liabilities, at Fair Value | (36) | (203) |
Commodity Derivatives - Natural Gas [Member] | Fixed Swaps/Futures [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Commodity Derivatives - Natural Gas [Member] | Fixed Swaps/Futures [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Commodity Derivatives - Natural Gas [Member] | Forward Physical Swaps [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | 2 | 4 |
Price Risk Derivative Liabilities, at Fair Value | (1) | |
Commodity Derivatives - Natural Gas [Member] | Forward Physical Swaps [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | |
Commodity Derivatives - Natural Gas [Member] | Forward Physical Swaps [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | 2 | 4 |
Price Risk Derivative Liabilities, at Fair Value | (1) | |
Commodity Derivatives - Natural Gas [Member] | Forward Physical Swaps [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | |
Commodity Derivatives - Power [Member] | Forward Swaps [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | 6 | 22 |
Price Risk Derivative Liabilities, at Fair Value | (4) | (22) |
Commodity Derivatives - Power [Member] | Forward Swaps [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Commodity Derivatives - Power [Member] | Forward Swaps [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | 6 | 22 |
Price Risk Derivative Liabilities, at Fair Value | (4) | (22) |
Commodity Derivatives - Power [Member] | Forward Swaps [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Commodity Derivatives - Power [Member] | Options - Calls [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | 1 | 1 |
Price Risk Derivative Liabilities, at Fair Value | (2) | |
Commodity Derivatives - Power [Member] | Options - Calls [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | 1 | 1 |
Price Risk Derivative Liabilities, at Fair Value | (2) | |
Commodity Derivatives - Power [Member] | Options - Calls [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | |
Commodity Derivatives - Power [Member] | Options - Calls [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | |
Commodity Derivatives - Power [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | | 3 |
Price Risk Derivative Liabilities, at Fair Value | | (2) |
Commodity Derivatives - Power [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | | 3 |
Price Risk Derivative Liabilities, at Fair Value | | (2) |
Commodity Derivatives - Power [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | | 0 |
Price Risk Derivative Liabilities, at Fair Value | | 0 |
Commodity Derivatives - Power [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | | 0 |
Price Risk Derivative Liabilities, at Fair Value | | 0 |
Commodity Derivatives - Power [Member] | Options - Puts [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | | 1 |
Price Risk Derivative Liabilities, at Fair Value | | (1) |
Commodity Derivatives - Power [Member] | Options - Puts [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | | 1 |
Price Risk Derivative Liabilities, at Fair Value | | (1) |
Commodity Derivatives - Power [Member] | Options - Puts [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | | 0 |
Price Risk Derivative Liabilities, at Fair Value | | 0 |
Commodity Derivatives - Power [Member] | Options - Puts [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | | 0 |
Price Risk Derivative Liabilities, at Fair Value | | 0 |
Commodity Derivatives - NGLs [Member] | Forward Swaps [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | 85 | 99 |
Price Risk Derivative Liabilities, at Fair Value | (114) | (89) |
Commodity Derivatives - NGLs [Member] | Forward Swaps [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | 85 | 99 |
Price Risk Derivative Liabilities, at Fair Value | (114) | (89) |
Commodity Derivatives - NGLs [Member] | Forward Swaps [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Commodity Derivatives - NGLs [Member] | Forward Swaps [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Commodity Derivatives - Refined Products [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | 7 | 9 |
Price Risk Derivative Liabilities, at Fair Value | (16) | |
Commodity Derivatives - Refined Products [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | 7 | 9 |
Price Risk Derivative Liabilities, at Fair Value | (16) | |
Commodity Derivatives - Refined Products [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | |
Commodity Derivatives - Refined Products [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | |
Commodity Derivatives - Crude [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | | |
Price Risk Derivative Assets, at Fair Value | 8 | 9 |
Price Risk Derivative Liabilities, at Fair Value | (8) | (5) |
Commodity Derivatives - Crude [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 | | |
Price Risk Derivative Assets, at Fair Value | 8 | 9 |
Price Risk Derivative Liabilities, at Fair Value | (8) | (5) |
Commodity Derivatives - Crude [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | 0 | 0 |
Commodity Derivatives - Crude [Member] | Future [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 | | |
Price Risk Derivative Assets, at Fair Value | 0 | 0 |
Price Risk Derivative Liabilities, at Fair Value | $ 0 | $ 0 |