Investment Securities

3 Months Ended

Mar. 31, 2025

Investments, Debt and Equity Securities [Abstract]

Investment Securities. Investment securities we hold are recorded at fair value in the accompanying consolidated balance sheets. We apply regulated operations accounting to the unrealized gains and losses of all investment securities. All realized and unrealized gains and losses are determined using the specific identification method.

The following tables summarize debt and equity securities as of March 31, 2025 and December 31, 2024.


	Gross Unrealized
	(dollars in thousands)
March 31, 2025	Cost		Gains		Losses		Fair Value
Equity	$	410,316	$	217,254	$	(5,760)	$	621,810
Debt	855,540		5,535		(11,816)		849,259
Other	10,324		401		(358)		10,367
Total	$	1,276,180	$	223,190	$	(17,934)	$	1,481,436


	Gross Unrealized
	(dollars in thousands)
December 31, 2024	Cost		Gains		Losses		Fair Value
Equity	$	259,554	$	231,815	$	(6,385)	$	484,984
Debt	864,575		3,209		(17,336)		850,448
Other	155,802		224		(96)		155,930
Total	$	1,279,931	$	235,248	$	(23,817)	$	1,491,362

The cost basis of our debt securities that were in unrealized loss positions at March 31, 2025 was $601,694,000. At March 31, 2025, $1,532,000 of the $11,816,000 of unrealized losses relates to securities that have been in unrealized loss positions for less than twelve months and $10,284,000 relates to securities that have been in unrealized loss positions for greater than twelve months. These unrealized losses are primarily attributable to increases in market interest rates.

The cost basis of our debt securities that were in unrealized loss positions at December 31, 2024 was $688,233,000. At December 31, 2024, $2,874,000 of the $17,336,000 of unrealized losses relates to securities that have been in unrealized loss positions for less than twelve months and $14,462,000 relates to securities that have been in unrealized loss positions for greater than twelve months. These unrealized losses are primarily attributable to increases in market interest rates.