Condensed Consolidated Statements of Changes in Equity - Piedmont - USD ($) $ in Millions	Total	Common Stock	Retained Earnings	Total Equity	Noncontrolling Interests	Piedmont	Piedmont Common Stock	Piedmont Retained Earnings	Piedmont Total Equity	Piedmont Noncontrolling Interests
Beginning Balance (Attributable to Parent) at Dec. 31, 2021		$ 1	$ 3,265	$ 49,296			$ 1,635	$ 1,714	$ 3,349
Beginning Balance (Attributable to Noncontrolling Interest) at Dec. 31, 2021					$ 1,840					$ 0
Beginning Balance (Parent) at Dec. 31, 2021	$ 51,136					$ 3,349
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,113					180		180	180
Ending Balance (Attributable to Parent) at Sep. 30, 2022		1	4,063	50,345			1,635	1,894	3,529
Ending Balance (Attributable to Noncontrolling Interest) at Sep. 30, 2022					1,824					0
Ending Balance (Parent) at Sep. 30, 2022	52,169					3,529
Beginning Balance (Attributable to Parent) at Jun. 30, 2022		1	3,457	49,720			1,635	1,927	3,562
Beginning Balance (Attributable to Noncontrolling Interest) at Jun. 30, 2022					1,864					0
Beginning Balance (Parent) at Jun. 30, 2022	51,584					3,562
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,413					(33)		(33)	(33)
Ending Balance (Attributable to Parent) at Sep. 30, 2022		1	4,063	50,345			1,635	1,894	3,529
Ending Balance (Attributable to Noncontrolling Interest) at Sep. 30, 2022					1,824					0
Ending Balance (Parent) at Sep. 30, 2022	52,169					3,529
Beginning Balance (Attributable to Parent) at Dec. 31, 2022	49,322	1	2,637	49,322		3,672	1,635	2,037	3,672
Beginning Balance (Attributable to Noncontrolling Interest) at Dec. 31, 2022	2,531				2,531	1				1
Beginning Balance (Parent) at Dec. 31, 2022	51,853					3,673
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,878					221		221	221
Ending Balance (Attributable to Parent) at Sep. 30, 2023	49,006	1	2,036	49,006		3,893	1,635	2,258	3,893
Ending Balance (Attributable to Noncontrolling Interest) at Sep. 30, 2023	2,820				2,820	1				1
Ending Balance (Parent) at Sep. 30, 2023	51,826					3,894
Beginning Balance (Attributable to Parent) at Jun. 30, 2023		1	1,615	48,333			1,635	2,272	3,907
Beginning Balance (Attributable to Noncontrolling Interest) at Jun. 30, 2023					2,738					1
Beginning Balance (Parent) at Jun. 30, 2023	51,071					3,908
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,321					(14)		(14)	(14)
Ending Balance (Attributable to Parent) at Sep. 30, 2023	49,006	$ 1	$ 2,036	$ 49,006		3,893	$ 1,635	$ 2,258	$ 3,893
Ending Balance (Attributable to Noncontrolling Interest) at Sep. 30, 2023	2,820				$ 2,820	1				$ 1
Ending Balance (Parent) at Sep. 30, 2023	$ 51,826					$ 3,894