Commitments, Guarantees and Contingencies - Clean Air Act and Climate Change (Details) $ in Millions			9 Months Ended	12 Months Ended		60 Months Ended
	Oct. 01, 2015	Aug. 03, 2015 T	Sep. 30, 2016	Dec. 31, 2016 USD ($) phase T	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($) T	Nov. 12, 2014
Loss Contingencies [Line Items]
Proposed reduction in power plants carbon pollution (percent)			90.00%
FES
Loss Contingencies [Line Items]
Amount of damages paid					$ 70
National Ambient Air Quality Standards
Loss Contingencies [Line Items]
Capping of SO2 Emissions Under CSAPR | T				2,400,000
Capping of NOx emissions under CSAPR | T				1,200,000
National Ambient Air Quality Standards | CSAPR
Loss Contingencies [Line Items]
Number of phases under the EPA’s CAIR for reductions of Sulfur Dioxide and Mono-Nitrogen Oxides | phase				2
Hazardous Air Pollutant Emissions
Loss Contingencies [Line Items]
Potential cost of compliance, MATS				$ 345		$ 345
Hazardous Air Pollutant Emissions | CES
Loss Contingencies [Line Items]
Potential cost of compliance, MATS				168		168
Hazardous Air Pollutant Emissions | Regulated Distribution
Loss Contingencies [Line Items]
Potential cost of compliance, MATS				$ 177		177
Caa Compliance
Loss Contingencies [Line Items]
Loss in period						$ 286
Mass remaining under contract | T				5,500,000		5,500,000
Caa Compliance | CES
Loss Contingencies [Line Items]
Loss in period						$ 125
Caa Compliance | Regulated Distribution
Loss Contingencies [Line Items]
Loss in period						$ 161
Mercury and Air Toxic Standards | FG | Certain Coal-Fired Power Plant
Loss Contingencies [Line Items]
Contractual amount in dispute (in T) | T		3,500,000.0
Mercury and Air Toxic Standards | FG | Another Coal-Fired Power Plant
Loss Contingencies [Line Items]
Contractual amount in dispute (in T) | T		2,500,000.0
Minimum | Climate Change
Loss Contingencies [Line Items]
Reduction in emissions (percent)							26.00%
Maximum | Climate Change
Loss Contingencies [Line Items]
Reduction in emissions (percent)							28.00%
EPA | Caa Compliance
Loss Contingencies [Line Items]
Period of time to implement plan	3 years
Signal Peak, Global Rail and Affiliates | Senior Secured Term Loan | Senior Loans | Global Holding
Loss Contingencies [Line Items]
Investment ownership percentage				69.99%		69.99%