Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Accumulated Amortization	$ 235	$ 186
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	1,500,000,000	1,500,000,000
Southern Power
Accumulated Amortization	$ 61	$ 47
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000,000	1,000,000
Common stock, shares outstanding (in shares)	1,000	1,000
Southern Power | 1.95% due 2019
Fixed stated interest rate of debt obligation	1.95%	1.95%
Southern Power | 2.375% due 2020
Fixed stated interest rate of debt obligation	2.375%	2.375%
Southern Power | 2.50% due 2021
Fixed stated interest rate of debt obligation	2.50%	2.50%
Southern Power | 1.00% due 2022
Fixed stated interest rate of debt obligation	1.00%	1.00%
Southern Company Gas
Accumulated Amortization	$ 145	$ 120
Common stock, par value (in dollars per share)	$ 0.01	$ 10,000.00
Common stock, shares authorized (in shares)	100,000,000	100
Common stock, shares outstanding (in shares)	100	100
Minimum | Southern Power | 1.85% to 5.25% due 2025-2046
Fixed stated interest rate of debt obligation	1.85%	1.85%
Maximum | Southern Power | 1.85% to 5.25% due 2025-2046
Fixed stated interest rate of debt obligation	5.25%	5.25%