Investment Securities - Available-for-sale Securities with Unrealized Loss (Details) $ in Thousands	Sep. 30, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	$ 169,408	$ 299,453
Less than 12 months, unrealized loss	$ 9,454	$ 12,051
Less than 12 months, Number of securities | security	236	254
12 months or more, fair value	$ 837,356	$ 803,481
12 months or more, unrealized loss	$ 184,491	$ 158,373
12 months or more, Number of securities | security	446	308
Total fair value	$ 1,006,764	$ 1,102,934
Total unrealized loss	193,945	170,424
U.S. Treasury and government agencies
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	15,992	112,730
Less than 12 months, unrealized loss	$ 374	$ 2,772
Less than 12 months, Number of securities | security	19	13
12 months or more, fair value	$ 26,476	$ 39,692
12 months or more, unrealized loss	$ 2,367	$ 3,279
12 months or more, Number of securities | security	12	11
Total fair value	$ 42,468	$ 152,422
Total unrealized loss	2,741	6,051
U.S. government sponsored agencies
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	29,514	15,166
Less than 12 months, unrealized loss	$ 450	$ 249
Less than 12 months, Number of securities | security	17	17
12 months or more, fair value	$ 74,418	$ 66,706
12 months or more, unrealized loss	$ 13,766	$ 13,407
12 months or more, Number of securities | security	17	18
Total fair value	$ 103,932	$ 81,872
Total unrealized loss	14,216	13,656
States and political subdivisions
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	47,093	60,324
Less than 12 months, unrealized loss	$ 3,358	$ 714
Less than 12 months, Number of securities | security	106	114
12 months or more, fair value	$ 170,282	$ 156,900
12 months or more, unrealized loss	$ 39,189	$ 35,028
12 months or more, Number of securities | security	156	117
Total fair value	$ 217,375	$ 217,224
Total unrealized loss	42,547	35,742
Residential mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	68,958	104,959
Less than 12 months, unrealized loss	$ 4,928	$ 8,087
Less than 12 months, Number of securities | security	85	105
12 months or more, fair value	$ 519,488	$ 488,452
12 months or more, unrealized loss	$ 117,194	$ 95,302
12 months or more, Number of securities | security	238	139
Total fair value	$ 588,446	$ 593,411
Total unrealized loss	122,122	103,389
Commercial mortgage-backed securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	7,851	1,874
Less than 12 months, unrealized loss	$ 344	$ 129
Less than 12 months, Number of securities | security	9	2
12 months or more, fair value	$ 42,767	$ 48,175
12 months or more, unrealized loss	$ 11,400	$ 10,913
12 months or more, Number of securities | security	21	21
Total fair value	$ 50,618	$ 50,049
Total unrealized loss	11,744	11,042
Bank-issued trust preferred securities
Available-for-sale securities that had an unrealized loss:
Less than 12 months, fair value	0	4,400
Less than 12 months, unrealized loss	$ 0	$ 100
Less than 12 months, Number of securities | security	0	3
12 months or more, fair value	$ 3,925	$ 3,556
12 months or more, unrealized loss	$ 575	$ 444
12 months or more, Number of securities | security	2	2
Total fair value	$ 3,925	$ 7,956
Total unrealized loss	$ 575	$ 544