Fair Value Measurements and Credit Concentration (Nonrecurring Fair Value Measurements) (Details) - Nonrecurring - USD ($) $ in Millions				1 Months Ended	9 Months Ended
		Sep. 30, 2015	Mar. 31, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014
Kerr Dam Project
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Pre-tax loss				$ 18		$ 18	[1]
Sapphire Portfolio and C.P. Crane Plant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Pre-tax loss	[1]				$ 122
Carrying Amount | Kerr Dam Project
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Nonrecurring measurement asset value	[2]		$ 47	47
Carrying Amount | Sapphire Portfolio and C.P. Crane Plant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Nonrecurring measurement asset value	[2]	$ 388			388
Level 3 | Kerr Dam Project
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Nonrecurring measurement asset value						$ 29
Fair value of net asset and (liability)			$ 29	$ 29
Level 3 | Sapphire Portfolio and C.P. Crane Plant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Nonrecurring measurement asset value	[3]	266			266
Fair value of net asset and (liability)		$ 266			$ 266
Discounted Cash Flow | Minimum | Level 3 | Kerr Dam Project
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Proprietary model used to calculate plant value	[4]		38.00%
Discounted Cash Flow | Minimum | Level 3 | Sapphire Portfolio and C.P. Crane Plant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Proprietary model used to calculate plant value	[4]	100.00%
Discounted Cash Flow | Maximum | Level 3 | Kerr Dam Project
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Proprietary model used to calculate plant value	[4]		38.00%
Discounted Cash Flow | Maximum | Level 3 | Sapphire Portfolio and C.P. Crane Plant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Proprietary model used to calculate plant value	[4]	100.00%
Discounted Cash Flow | Weighted Average | Level 3 | Kerr Dam Project
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Proprietary model used to calculate plant value	[4]		38.00%
Discounted Cash Flow | Weighted Average | Level 3 | Sapphire Portfolio and C.P. Crane Plant
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Proprietary model used to calculate plant value	[4]	100.00%

[1] The impairments on the Kerr Dam Project and Sapphire portfolio are included in "Income (Loss) from Discontinued Operations (net of income taxes)" on the Statement of Income. The impairment on the C.P. Crane plant is included in "Impairments" on the Statement of Income.

[2] Represents carrying value before fair value measurement.

[3] For the Sapphire portfolio, also reflects estimated cost to sell.

[4] The range and weighted average represent the percentage of fair value derived from the unobservable inputs.