Investment Securities - Unrealized Gross Losses and Fair Values of Securities in a Continuous Loss Position (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2023 USD ($) security shares	Dec. 31, 2022 USD ($) security shares
Securities in the available-for-sale portfolio in a continuous loss position
Number of individual securities in a continuous loss position | security	279	275
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses	$ (973,000)	$ (213,696,000)
12 Months or More Unrealized Losses	(448,375,000)	(184,820,000)
Total Unrealized Losses	(449,348,000)	(398,516,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value	75,258,000	2,023,259,000
12 Months or More Fair Value	2,645,713,000	1,056,595,000
Total Fair Value	2,720,971,000	3,079,854,000
Allowance for credit losses, investment securities	$ 0	$ 0
Investment securities comprised of collateralized loan obligations rated AA or better and obligations issued by local state and political subdivisions rated AA or better	5.00%	5.00%
Class B restricted shares | Visa
Time in Continuous Loss, Fair Value
Shares held | shares	120,000	120,000
Cost basis	$ 0	$ 0
U.S. Treasury and government agency debt securities
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses		(2,962,000)
12 Months or More Unrealized Losses	(12,105,000)	(9,365,000)
Total Unrealized Losses	(12,105,000)	(12,327,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value		83,870,000
12 Months or More Fair Value	114,159,000	67,112,000
Total Fair Value	114,159,000	150,982,000
Government-sponsored enterprises debt securities
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses		(699,000)
12 Months or More Unrealized Losses	(740,000)
Total Unrealized Losses	(740,000)	(699,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value		44,301,000
12 Months or More Fair Value	19,260,000
Total Fair Value	19,260,000	44,301,000
Residential - Government-sponsored enterprises
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses		(73,954,000)
12 Months or More Unrealized Losses	(179,487,000)	(83,309,000)
Total Unrealized Losses	(179,487,000)	(157,263,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value		645,338,000
12 Months or More Fair Value	1,005,782,000	515,117,000
Total Fair Value	1,005,782,000	1,160,455,000
Residential - Government agency
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses		(7,069,000)
12 Months or More Unrealized Losses	(9,406,000)
Total Unrealized Losses	(9,406,000)	(7,069,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value		59,723,000
12 Months or More Fair Value	52,362,000
Total Fair Value	52,362,000	59,723,000
Commercial - Government agency
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses		(15,852,000)
12 Months or More Unrealized Losses	(60,535,000)	(28,995,000)
Total Unrealized Losses	(60,535,000)	(44,847,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value		108,842,000
12 Months or More Fair Value	211,897,000	129,011,000
Total Fair Value	211,897,000	237,853,000
Commercial - Government-sponsored enterprises
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses		(7,348,000)
12 Months or More Unrealized Losses	(9,101,000)	(3,691,000)
Total Unrealized Losses	(9,101,000)	(11,039,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value		94,657,000
12 Months or More Fair Value	84,920,000	24,916,000
Total Fair Value	84,920,000	119,573,000
Commercial - Non -agency
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses		(493,000)
12 Months or More Unrealized Losses	(362,000)
Total Unrealized Losses	(362,000)	(493,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value		21,471,000
12 Months or More Fair Value	21,602,000
Total Fair Value	21,602,000	21,471,000
Government agency
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses		(74,797,000)
12 Months or More Unrealized Losses	(95,355,000)	(10,405,000)
Total Unrealized Losses	(95,355,000)	(85,202,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value		596,907,000
12 Months or More Fair Value	565,852,000	56,415,000
Total Fair Value	565,852,000	653,322,000
Government-sponsored enterprises
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses		(21,916,000)
12 Months or More Unrealized Losses	(78,469,000)	(49,055,000)
Total Unrealized Losses	(78,469,000)	(70,971,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value		198,108,000
12 Months or More Fair Value	400,748,000	264,024,000
Total Fair Value	400,748,000	462,132,000
Collateralized Loan Obligations
Time in Continuous Loss, Unrealized Losses
Less Than 12 Months Unrealized Losses	(973,000)	(8,606,000)
12 Months or More Unrealized Losses	(2,815,000)
Total Unrealized Losses	(3,788,000)	(8,606,000)
Time in Continuous Loss, Fair Value
Less Than 12 Months, Fair Value	75,258,000	170,042,000
12 Months or More Fair Value	169,131,000
Total Fair Value	$ 244,389,000	$ 170,042,000