Securities- Unrealized Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 1,670,744	$ 407,150
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	21,564	4,277
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	384,332	464,283
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	8,357	13,560
Total investments with an unrealized loss, fair value	2,055,076	871,433
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	29,921	17,837
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	132,157	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	230	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Total investments with an unrealized loss, fair value	132,157	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	230	0
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	195,921	9,962
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,552	38
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	14,807	6,091
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	440	22
Total investments with an unrealized loss, fair value	210,728	16,053
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	2,992	60
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	633,938	165,696
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	8,630	1,772
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	114,968	35,997
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3,270	555
Total investments with an unrealized loss, fair value	748,906	201,693
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	11,900	2,327
State and municipal securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	523,859	175,115
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	9,138	2,220
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	222,884	345,435
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,961	10,264
Total investments with an unrealized loss, fair value	746,743	520,550
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	12,099	12,484
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	166,457	46,399
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	592	207
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	6,703	52,840
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	141	450
Total investments with an unrealized loss, fair value	173,160	99,239
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	733	657
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	18,412	9,978
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	422	40
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	24,970	23,920
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,545	2,269
Total investments with an unrealized loss, fair value	43,382	33,898
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	$ 1,967	$ 2,309

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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