Securities - Fair Value and Age of Gross Unrealized Losses of Debt Securities (Details) $ in Thousands	Sep. 30, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months | security	28	116
Fair Value, Less Than 12 Months	$ 136,557	$ 663,656
Unrealized Losses, Less Than 12 Months	$ (4,384)	$ (46,120)
Number of Securities, 12 Months or More | security	121	31
Fair Value, 12 Months or More	$ 817,710	$ 308,067
Unrealized Losses, 12 Months or More	$ (111,044)	$ (56,462)
Number of Securities, Total | security	149	147
Fair Value, Total	$ 954,267	$ 971,723
Unrealized Losses, Total	$ (115,428)	$ (102,582)
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months | security	1	6
Fair Value, Less Than 12 Months	$ 9,895	$ 57,057
Unrealized Losses, Less Than 12 Months	$ (203)	$ (3,363)
Number of Securities, 12 Months or More | security	13	8
Fair Value, 12 Months or More	$ 120,142	$ 74,638
Unrealized Losses, 12 Months or More	$ (14,335)	$ (10,358)
Number of Securities, Total | security	14	14
Fair Value, Total	$ 130,037	$ 131,695
Unrealized Losses, Total	$ (14,538)	$ (13,721)
Obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months | security	0	6
Fair Value, Less Than 12 Months	$ 0	$ 41,811
Unrealized Losses, Less Than 12 Months	$ 0	$ (1,668)
Number of Securities, 12 Months or More | security	6	0
Fair Value, 12 Months or More	$ 42,049	$ 0
Unrealized Losses, 12 Months or More	$ (1,328)	$ 0
Number of Securities, Total | security	6	6
Fair Value, Total	$ 42,049	$ 41,811
Unrealized Losses, Total	$ (1,328)	$ (1,668)
Collateralized mortgage obligations of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months | security	8	47
Fair Value, Less Than 12 Months	$ 78,608	$ 296,509
Unrealized Losses, Less Than 12 Months	$ (2,402)	$ (28,153)
Number of Securities, 12 Months or More | security	57	13
Fair Value, 12 Months or More	$ 351,370	$ 112,902
Unrealized Losses, 12 Months or More	$ (60,979)	$ (25,682)
Number of Securities, Total | security	65	60
Fair Value, Total	$ 429,978	$ 409,411
Unrealized Losses, Total	$ (63,381)	$ (53,835)
Residential mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months | security	12	25
Fair Value, Less Than 12 Months	$ 319	$ 7,143
Unrealized Losses, Less Than 12 Months	$ (7)	$ (589)
Number of Securities, 12 Months or More | security	14	3
Fair Value, 12 Months or More	$ 36,567	$ 34,223
Unrealized Losses, 12 Months or More	$ (8,909)	$ (7,245)
Number of Securities, Total | security	26	28
Fair Value, Total	$ 36,886	$ 41,366
Unrealized Losses, Total	$ (8,916)	$ (7,834)
Commercial mortgage-backed securities of U.S. government corporations and agencies
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months | security	2	30
Fair Value, Less Than 12 Months	$ 18,525	$ 241,009
Unrealized Losses, Less Than 12 Months	$ (591)	$ (11,975)
Number of Securities, 12 Months or More | security	31	7
Fair Value, 12 Months or More	$ 267,582	$ 86,304
Unrealized Losses, 12 Months or More	$ (25,493)	$ (13,177)
Number of Securities, Total | security	33	37
Fair Value, Total	$ 286,107	$ 327,313
Unrealized Losses, Total	$ (26,084)	$ (25,152)
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Number of Securities, Less Than 12 Months | security	5	2
Fair Value, Less Than 12 Months	$ 29,210	$ 20,127
Unrealized Losses, Less Than 12 Months	$ (1,181)	$ (372)
Number of Securities, 12 Months or More | security	0	0
Fair Value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of Securities, Total | security	5	2
Fair Value, Total	$ 29,210	$ 20,127
Unrealized Losses, Total	$ (1,181)	$ (372)