Investment Securities - HTM Debt Securities in Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Summary of HTM debt securities in an unrealized loss position
Fair Value, Less than 12 Months	$ 5,229	$ 25,507
Unrealized Loss, Less than 12 Months	12	2,127
Fair Value, 12 Months or More	1,919,303	1,915,136
Unrealized Loss, 12 Months or More	337,092	421,865
Fair Value, Total	1,924,532	1,940,643
Unrealized Loss, Total	337,104	423,992
U.S. Treasuries
Summary of HTM debt securities in an unrealized loss position
Fair Value, Less than 12 Months	0	0
Unrealized Loss, Less than 12 Months	0	0
Fair Value, 12 Months or More	18,880	18,162
Unrealized Loss, 12 Months or More	1,039	1,734
Fair Value, Total	18,880	18,162
Unrealized Loss, Total	1,039	1,734
U.S. Government Agencies & GSEs
Summary of HTM debt securities in an unrealized loss position
Fair Value, Less than 12 Months	0	0
Unrealized Loss, Less than 12 Months	0	0
Fair Value, 12 Months or More	87,071	82,863
Unrealized Loss, 12 Months or More	11,713	16,291
Fair Value, Total	87,071	82,863
Unrealized Loss, Total	11,713	16,291
State and political subdivisions
Summary of HTM debt securities in an unrealized loss position
Fair Value, Less than 12 Months	5,229	18,729
Unrealized Loss, Less than 12 Months	12	305
Fair Value, 12 Months or More	222,344	212,356
Unrealized Loss, 12 Months or More	46,315	54,901
Fair Value, Total	227,573	231,085
Unrealized Loss, Total	46,327	55,206
Residential MBS, Agency & GSEs
Summary of HTM debt securities in an unrealized loss position
Fair Value, Less than 12 Months	0	6,778
Unrealized Loss, Less than 12 Months	0	1,822
Fair Value, 12 Months or More	1,032,380	1,051,455
Unrealized Loss, 12 Months or More	172,538	221,849
Fair Value, Total	1,032,380	1,058,233
Unrealized Loss, Total	172,538	223,671
Commercial MBS, Agency & GSEs
Summary of HTM debt securities in an unrealized loss position
Fair Value, Less than 12 Months	0	0
Unrealized Loss, Less than 12 Months	0	0
Fair Value, 12 Months or More	545,567	537,981
Unrealized Loss, 12 Months or More	103,548	124,409
Fair Value, Total	545,567	537,981
Unrealized Loss, Total	103,548	124,409
Supranational entities
Summary of HTM debt securities in an unrealized loss position
Fair Value, Less than 12 Months	0	0
Unrealized Loss, Less than 12 Months	0	0
Fair Value, 12 Months or More	13,061	12,319
Unrealized Loss, 12 Months or More	1,939	2,681
Fair Value, Total	13,061	12,319
Unrealized Loss, Total	$ 1,939	$ 2,681

UNITED COMMUNITY BANKS INC 10-Q