Common Equity - Changes in outstanding common shares (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Common Equity.
Beginning balance	20,172,746	20,335,934	20,059,390
Treasury stock purchases	(184,964)	(559,945)	(147,785)
Common stock issued (including share-based compensation impact)	322,802	396,757	424,329
Ending balance	20,310,584	20,172,746	20,335,934