Securities- Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 1,034,351	$ 1,021,511
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	7,651	14,349
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,212,316	2,243,962
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	255,111	243,875
Total investments with an unrealized loss, fair value	3,246,667	3,265,473
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	262,762	258,224
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	669,265	693,621
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,780	11,651
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	130,101	192,500
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	599	2,929
Total investments with an unrealized loss, fair value	799,366	886,121
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	4,379	14,580
U.S. Government agency securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,428	14,989
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	13	11
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	286,532	247,648
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	27,463	21,866
Total investments with an unrealized loss, fair value	287,960	262,637
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	27,476	21,877
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	43,474	72,907
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	615	1,518
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	799,688	828,251
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	125,556	123,499
Total investments with an unrealized loss, fair value	843,162	901,158
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	126,171	125,017
State and municipal securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	254,269	185,108
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,053	908
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	500,627	449,212
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	51,940	44,200
Total investments with an unrealized loss, fair value	754,896	634,320
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	53,993	45,108
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	39,732	42,207
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	91	254
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	120,109	122,469
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	8,802	10,026
Total investments with an unrealized loss, fair value	159,841	164,676
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	8,893	10,280
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	26,183	12,679
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,099	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	375,259	403,882
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	40,751	41,355
Total investments with an unrealized loss, fair value	401,442	416,561
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	$ 41,850	$ 41,362