Income Tax (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Taxes Disclosure [Line Items]
Income taxes on operating income	$ 227,000,000	$ 164,000,000
Effective tax rate	37.00%	35.00%
Deferred tax asset, net operating loss	$ 22,000,000
Valuation allowance	0
Estimated liability for uncertain tax positions	40,000,000
Effective income tax rate reconciliation, uncertainty of taxes	33,000,000
Effective income tax rate reconciliation, uncertainty net of federal taxes	23,000,000
Unrecognized tax benefits that would have an impact on effective tax rate	19,000,000
Unrecognized tax benefits that would have an impact on effective tax rate, net of taxes	13,000,000
Total amount of unrecognized tax benefits, if recognized, that would reduce effective tax rate	23,000,000
Total amount of unrecognized tax benefits, if recognized, that would reduce effective tax rate, net of federal taxes	16,000,000
Penalties for uncertain tax positions	0
CECONY
Income Taxes Disclosure [Line Items]
Income taxes on operating income	$ 218,000,000	$ 180,000,000
Effective tax rate	39.00%	37.00%
Estimated liability for uncertain tax positions	$ 21,000,000
Effective income tax rate reconciliation, uncertainty of taxes	17,000,000
Effective income tax rate reconciliation, uncertainty net of federal taxes	12,000,000
Unrecognized tax benefits that would have an impact on effective tax rate	$ 2,000,000