v3.26.1
Investment Securities
 6 Months Ended
Jun. 30, 2026
Investments, Debt and Equity Securities [Abstract]  
Investment Securities 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 June 30, 2026 and December 31, 2025.
Gross Unrealized
(dollars in thousands)
June 30, 2026CostGainsLossesFair
Value
Equity$420,541 $396,783 $(4,921)$812,403 
Debt819,701 10,100 (11,797)818,004 
Other15,284 685 (424)15,545 
Total$1,255,526 $407,568 $(17,142)$1,645,952 
Gross Unrealized
(dollars in thousands)
December 31, 2025CostGainsLossesFair
Value
Equity$407,059 $313,033 $(4,440)$715,652 
Debt850,056 10,509 (9,398)851,167 
Other22,506 205 (878)21,833 
Total$1,279,621 $323,747 $(14,716)$1,588,652 

The cost basis of our debt securities that were in unrealized loss positions at June 30, 2026 was $610,379,000. At June 30, 2026, $2,190,000 of the $11,797,000 of unrealized losses relates to securities that have been in unrealized loss positions for less than twelve months and $9,607,000 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 following our purchase of these securities.

The cost basis of our debt securities that were in unrealized loss positions at December 31, 2025 was $324,301,000. At December 31, 2025, $1,178,000 of the $9,398,000 of unrealized losses relates to securities that have been in unrealized loss positions for less than twelve months and $8,220,000 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 following our purchase of these securities.