Securities - Gross Unrealized Losses and Fair Value by Investment Category (Details) $ in Thousands	Jun. 30, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Available for Sale:
Number of positions, Less than 12 Months | security	18	247
Fair Value, Less than 12 Months	$ 21,123	$ 726,431
Unrealized Losses, Less than 12 Months	$ (1,241)	$ (41,924)
Number of positions, 12 Months or More | security	143	98
Fair value, 12 Months or More	$ 889,083	$ 788,657
Unrealized Losses, 12 Months or More	$ (178,308)	$ (159,375)
Number of positions | security	161	345
Fair Value	$ 910,206	$ 1,515,088
Unrealized Losses	$ (179,549)	$ (201,299)
Held to Maturity:
Number of positions, Less than 12 Months | security	130	122
Fair Value, Less than 12 Months	$ 312,387	$ 448,575
Unrealized Losses, Less than 12 Months	$ (45,730)	$ (51,436)
Number of positions, 12 Months or More | security	105	115
Fair Value, 12 Months or More	$ 837,063	$ 755,527
Unrealized Losses, 12 Months or More	$ (73,828)	$ (66,113)
Number of positions | security	235	237
Fair Value	$ 1,149,450	$ 1,204,102
Unrealized Losses	$ (119,558)	$ (117,549)
Obligations of other U.S. Government agencies and corporations
Available for Sale:
Number of positions, Less than 12 Months | security		5
Fair Value, Less than 12 Months		$ 164,660
Unrealized Losses, Less than 12 Months		$ (5,340)
Number of positions, 12 Months or More | security		0
Fair value, 12 Months or More		$ 0
Unrealized Losses, 12 Months or More		$ 0
Number of positions | security		5
Fair Value		$ 164,660
Unrealized Losses		$ (5,340)
Obligations of states and political subdivisions
Available for Sale:
Number of positions, Less than 12 Months | security	10	84
Fair Value, Less than 12 Months	$ 7,827	$ 96,939
Unrealized Losses, Less than 12 Months	$ (35)	$ (4,869)
Number of positions, 12 Months or More | security	10	11
Fair value, 12 Months or More	$ 23,073	$ 33,038
Unrealized Losses, 12 Months or More	$ (3,404)	$ (4,499)
Number of positions | security	20	95
Fair Value	$ 30,900	$ 129,977
Unrealized Losses	$ (3,439)	$ (9,368)
Held to Maturity:
Number of positions, Less than 12 Months | security	126	105
Fair Value, Less than 12 Months	$ 242,673	$ 191,442
Unrealized Losses, Less than 12 Months	$ (42,767)	$ (35,871)
Number of positions, 12 Months or More | security	1	24
Fair Value, 12 Months or More	$ 426	$ 49,697
Unrealized Losses, 12 Months or More	$ (15)	$ (12,454)
Number of positions | security	127	129
Fair Value	$ 243,099	$ 241,139
Unrealized Losses	$ (42,782)	$ (48,325)
Other debt securities
Available for Sale:
Number of positions, Less than 12 Months | security	3	25
Fair Value, Less than 12 Months	$ 5,492	$ 63,423
Unrealized Losses, Less than 12 Months	$ (800)	$ (3,167)
Number of positions, 12 Months or More | security	18	1
Fair value, 12 Months or More	$ 32,171	$ 7,412
Unrealized Losses, 12 Months or More	$ (4,869)	$ (883)
Number of positions | security	21	26
Fair Value	$ 37,663	$ 70,835
Unrealized Losses	$ (5,669)	$ (4,050)
Held to Maturity:
Number of positions, Less than 12 Months | security	0	2
Fair Value, Less than 12 Months	$ 0	$ 42,567
Unrealized Losses, Less than 12 Months	$ 0	$ (2,013)
Number of positions, 12 Months or More | security	10	8
Fair Value, 12 Months or More	$ 50,323	$ 16,042
Unrealized Losses, 12 Months or More	$ (5,058)	$ (2,253)
Number of positions | security	10	10
Fair Value	$ 50,323	$ 58,609
Unrealized Losses	$ (5,058)	$ (4,266)
Government agency mortgage backed securities | Residential mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months | security	4	97
Fair Value, Less than 12 Months	$ 6,673	$ 214,516
Unrealized Losses, Less than 12 Months	$ (368)	$ (15,115)
Number of positions, 12 Months or More | security	46	29
Fair value, 12 Months or More	$ 275,823	$ 237,970
Unrealized Losses, 12 Months or More	$ (42,383)	$ (36,921)
Number of positions | security	50	126
Fair Value	$ 282,496	$ 452,486
Unrealized Losses	$ (42,751)	$ (52,036)
Held to Maturity:
Number of positions, Less than 12 Months | security	2	8
Fair Value, Less than 12 Months	$ 39,028	$ 94,258
Unrealized Losses, Less than 12 Months	$ (1,387)	$ (4,186)
Number of positions, 12 Months or More | security	68	62
Fair Value, 12 Months or More	$ 395,220	$ 364,870
Unrealized Losses, 12 Months or More	$ (24,410)	$ (20,246)
Number of positions | security	70	70
Fair Value	$ 434,248	$ 459,128
Unrealized Losses	$ (25,797)	$ (24,432)
Government agency mortgage backed securities | Commercial mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months | security	0	4
Fair Value, Less than 12 Months	$ 0	$ 10,114
Unrealized Losses, Less than 12 Months	$ 0	$ (1,053)
Number of positions, 12 Months or More | security	2	0
Fair value, 12 Months or More	$ 5,245	$ 0
Unrealized Losses, 12 Months or More	$ (797)	$ 0
Number of positions | security	2	4
Fair Value	$ 5,245	$ 10,114
Unrealized Losses	$ (797)	$ (1,053)
Held to Maturity:
Number of positions, Less than 12 Months | security	0	1
Fair Value, Less than 12 Months	$ 0	$ 13,745
Unrealized Losses, Less than 12 Months	$ 0	$ (3,261)
Number of positions, 12 Months or More | security	1	0
Fair Value, 12 Months or More	$ 13,764	$ 0
Unrealized Losses, 12 Months or More	$ (3,231)	$ 0
Number of positions | security	1	1
Fair Value	$ 13,764	$ 13,745
Unrealized Losses	$ (3,231)	$ (3,261)
Government agency collateralized mortgage obligations | Residential mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months | security	0	16
Fair Value, Less than 12 Months	$ 0	$ 109,753
Unrealized Losses, Less than 12 Months	$ 0	$ (8,552)
Number of positions, 12 Months or More | security	41	36
Fair value, 12 Months or More	$ 415,090	$ 391,416
Unrealized Losses, 12 Months or More	$ (101,385)	$ (95,312)
Number of positions | security	41	52
Fair Value	$ 415,090	$ 501,169
Unrealized Losses	$ (101,385)	$ (103,864)
Held to Maturity:
Number of positions, Less than 12 Months | security	1	4
Fair Value, Less than 12 Months	$ 26,396	$ 98,912
Unrealized Losses, Less than 12 Months	$ (1,278)	$ (5,479)
Number of positions, 12 Months or More | security	17	14
Fair Value, 12 Months or More	$ 344,025	$ 293,698
Unrealized Losses, 12 Months or More	$ (34,094)	$ (25,227)
Number of positions | security	18	18
Fair Value	$ 370,421	$ 392,610
Unrealized Losses	$ (35,372)	$ (30,706)
Government agency collateralized mortgage obligations | Commercial mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months | security	1	16
Fair Value, Less than 12 Months	$ 1,131	$ 67,026
Unrealized Losses, Less than 12 Months	$ (38)	$ (3,828)
Number of positions, 12 Months or More | security	26	21
Fair value, 12 Months or More	$ 137,681	$ 118,821
Unrealized Losses, 12 Months or More	$ (25,470)	$ (21,760)
Number of positions | security	27	37
Fair Value	$ 138,812	$ 185,847
Unrealized Losses	$ (25,508)	$ (25,588)
Held to Maturity:
Number of positions, Less than 12 Months | security	1	2
Fair Value, Less than 12 Months	$ 4,290	$ 7,651
Unrealized Losses, Less than 12 Months	$ (298)	$ (626)
Number of positions, 12 Months or More | security	8	7
Fair Value, 12 Months or More	$ 33,305	$ 31,220
Unrealized Losses, 12 Months or More	$ (7,020)	$ (5,933)
Number of positions | security	9	9
Fair Value	$ 37,595	$ 38,871
Unrealized Losses	$ (7,318)	$ (6,559)