Securities- Unrealized Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 931,198	$ 1,456,921
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	30,681	77,421
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,670,913	1,550,911
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	375,231	248,005
Total investments with an unrealized loss, fair value	3,602,111	3,007,832
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	405,912	325,426
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	548,685	192,188
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,357	1,963
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	172,773	1,997
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	616	4
Total investments with an unrealized loss, fair value	721,458	194,185
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	2,973	1,967
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	26,468	46,062
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	280	2,224
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	228,637	350,094
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	29,354	34,094
Total investments with an unrealized loss, fair value	255,105	396,156
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	29,634	36,318
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	53,755	390,014
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,253	34,106
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	801,474	570,601
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	161,902	109,477
Total investments with an unrealized loss, fair value	855,229	960,615
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	164,155	143,583
State and municipal securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	221,897	568,691
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	24,286	18,863
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	989,360	304,451
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	114,999	59,694
Total investments with an unrealized loss, fair value	1,211,257	873,142
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	139,285	78,557
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	69,397	513
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,283	5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	93,719	116,442
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	13,470	16,978
Total investments with an unrealized loss, fair value	163,116	116,955
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	14,753	16,983
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	10,996	259,453
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	222	20,260
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	384,950	207,326
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	54,890	27,758
Total investments with an unrealized loss, fair value	395,946	466,779
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	$ 55,112	$ 48,018