Debt and Credit Facilities (Annual Maturities) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	$ 3,244,000,000	$ 2,319,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2018	3,244,000,000
2019	3,563,000,000
2020	3,699,000,000
2021	3,760,000,000
2022	3,010,000,000
Thereafter	33,271,000,000
Total long-term debt, including current maturities	50,547,000,000
Other Debt Obligations [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	544,000,000
Purchase Accounting Adjustments [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Purchase accounting adjustments	$ (1,732,000,000)
Parent Company [Member] | Unsecured Debt Maturing June 2018, 6.250% Coupon [Member] | Unsecured Debt [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	6.25%
Current maturities of long-term debt	$ 250,000,000
Parent Company [Member] | Unsecured Debt Maturing June 2018, 2.100% Coupon [Member] | Unsecured Debt [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	2.10%
Current maturities of long-term debt	$ 500,000,000
Duke Energy Carolinas [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	1,205,000,000	116,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2018	1,205,000,000
2019	6,000,000
2020	906,000,000
2021	502,000,000
2022	302,000,000
Thereafter	7,182,000,000
Total long-term debt, including current maturities	$ 10,103,000,000
Duke Energy Carolinas [Member] | First Mortgage Bonds Maturing January 2018, 5.250% Coupon [Member] | First Mortgage Bonds [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	5.25%
Current maturities of long-term debt	$ 400,000,000
Duke Energy Carolinas [Member] | First Mortgage Bonds Maturing April 2018, 5.100% Coupon [Member] | First Mortgage Bonds [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	5.10%
Current maturities of long-term debt	$ 300,000,000
Duke Energy Carolinas [Member] | First Mortgage Bonds Maturing November 2018 7.000% Coupon [Member] | First Mortgage Bonds [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	7.00%
Current maturities of long-term debt	$ 500,000,000
Progress Energy [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	771,000,000	778,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2018	771,000,000
2019	2,191,000,000
2020	871,000,000
2021	1,472,000,000
2022	1,176,000,000
Thereafter	11,356,000,000
Total long-term debt, including current maturities	17,837,000,000
Duke Energy Progress [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	3,000,000	452,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2018	3,000,000
2019	903,000,000
2020	304,000,000
2021	602,000,000
2022	653,000,000
Thereafter	4,892,000,000
Total long-term debt, including current maturities	7,357,000,000
Duke Energy Florida [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	768,000,000	326,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2018	768,000,000
2019	490,000,000
2020	568,000,000
2021	371,000,000
2022	74,000,000
Thereafter	4,824,000,000
Total long-term debt, including current maturities	$ 7,095,000,000
Duke Energy Florida [Member] | First Mortgage Bonds Maturing June 2018, 5.650% Coupon [Member] | First Mortgage Bonds [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	5.65%
Current maturities of long-term debt	$ 500,000,000
Duke Energy Ohio [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	3,000,000	1,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2018	3,000,000
2019	548,000,000
2021	48,000,000
2022	23,000,000
Thereafter	1,445,000,000
Total long-term debt, including current maturities	2,067,000,000
Duke Energy Indiana [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	3,000,000	3,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2018	3,000,000
2019	61,000,000
2020	502,000,000
2021	69,000,000
2022	243,000,000
Thereafter	2,905,000,000
Total long-term debt, including current maturities	3,783,000,000
Piedmont Natural Gas [Member]
Current Maturities Of Long Term Debt [Abstract]
Current maturities of long-term debt	250,000,000	$ 35,000,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2018	250,000,000
2021	159,000,000
Thereafter	1,628,000,000
Total long-term debt, including current maturities	$ 2,037,000,000
Piedmont Natural Gas [Member] | Unsecured Debt Maturing December 2018 Variable Rate [Member] | Unsecured Debt [Member]
Current Maturities Of Long Term Debt [Abstract]
Interest rate	2.286%
Current maturities of long-term debt	$ 250,000,000