Securities - Unrealized Losses on Available-for-Sale of Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	$ 473,204	$ 76,389
Unrealized Losses, Less than 12 Months	3,583	1,142
Fair Value, 12 Months or Longer	268,309	880,651
Unrealized Losses, 12 Months or Longer	19,440	138,284
Fair Value	741,513	957,040
Unrealized Losses	23,023	139,426
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	0	0
Unrealized Losses, Less than 12 Months	0	0
Fair Value, 12 Months or Longer	38,936	57,019
Unrealized Losses, 12 Months or Longer	1,925	3,784
Fair Value	38,936	57,019
Unrealized Losses	1,925	3,784
Obligations of U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	0	14,085
Unrealized Losses, Less than 12 Months	0	515
Fair Value, 12 Months or Longer	141,606	188,296
Unrealized Losses, 12 Months or Longer	11,653	19,861
Fair Value	141,606	202,381
Unrealized Losses	11,653	20,376
Obligations of U.S. states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	2,530	3,159
Unrealized Losses, Less than 12 Months	2	36
Fair Value, 12 Months or Longer	65,279	73,657
Unrealized Losses, 12 Months or Longer	5,212	8,602
Fair Value	67,809	76,816
Unrealized Losses	5,214	8,638
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	179,250	27,082
Unrealized Losses, Less than 12 Months	2,129	89
Fair Value, 12 Months or Longer	12,051	35,879
Unrealized Losses, 12 Months or Longer	228	4,790
Fair Value	191,301	62,961
Unrealized Losses	2,357	4,879
U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	291,424	32,063
Unrealized Losses, Less than 12 Months	1,452	502
Fair Value, 12 Months or Longer	7,990	523,353
Unrealized Losses, 12 Months or Longer	369	101,194
Fair Value	299,414	555,416
Unrealized Losses	1,821	101,696
U.S. corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	0	0
Unrealized Losses, Less than 12 Months	0	0
Fair Value, 12 Months or Longer	2,447	2,447
Unrealized Losses, 12 Months or Longer	53	53
Fair Value	2,447	2,447
Unrealized Losses	$ 53	$ 53

TOMPKINS FINANCIAL CORP 10-K