Long - Term Debt Present Value of Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Year One	$ 795,000
Year Two	1,358,159
Year Three	1,104,289
Year Four	1,865,154
Year Five	1,175,000
Long-term Debt, Fair Value	19,059,950	$ 16,101,455
Interest Expense, Debt	807,382	768,322	$ 707,212
Total Long-Term Debt	17,873,655	16,168,312
System Energy [Member]
Year One	0
Year Two	131,600
Year Three	134,000
Year Four	250,000
Year Five	0
Long-term Debt, Fair Value	565,209	630,475
Interest Expense, Debt	35,328	38,424	$ 37,141
Total Long-Term Debt	548,107	630,750
Grand Gulf [Member] | System Energy [Member]
Year One	17,188	17,188
Year Two	17,188	17,188
Year Three	17,188	17,188
Year Four	17,188	17,188
Year Five	17,188	17,188
Long-term Debt, Maturities, Repayments of Principal after Year Five	206,250	223,437
Long-term Debt, Fair Value	292,190	309,377
Interest Expense, Debt	257,844	275,025
Total Long-Term Debt	$ 34,346	$ 34,352