INVESTMENT SECURITIES - Investments' Gross Unrealized Losses and Fair Value Aggregated by Investment Category and Length of Time in Continuous Unrealized Loss Position (Details) $ in Thousands	Sep. 30, 2022 USD ($) security	Dec. 31, 2021 USD ($) security
Fair Value
Less than 12 Months	$ 1,517,710	$ 636,389
12 Months or Longer	441,601	8,829
Total	1,959,311	645,218
Gross Unrealized Losses
Less than 12 Months	266,056	13,239
12 Months or Longer	126,558	401
Total	$ 392,614	$ 13,640
Number of Securities | security	1,281	161
U.S. Treasury
Fair Value
Less than 12 Months	$ 2,067	$ 999
12 Months or Longer	0	0
Total	2,067	999
Gross Unrealized Losses
Less than 12 Months	40	1
12 Months or Longer	0	0
Total	$ 40	$ 1
Number of Securities | security	4	1
U.S. Government-sponsored agency securities
Fair Value
Less than 12 Months	$ 67,039	$ 68,524
12 Months or Longer	38,727	0
Total	105,766	68,524
Gross Unrealized Losses
Less than 12 Months	7,453	1,545
12 Months or Longer	8,688	0
Total	$ 16,141	$ 1,545
Number of Securities | security	17	8
State and municipal
Fair Value
Less than 12 Months	$ 1,229,682	$ 138,187
12 Months or Longer	90,765	505
Total	1,320,447	138,692
Gross Unrealized Losses
Less than 12 Months	234,780	894
12 Months or Longer	32,216	4
Total	$ 266,996	$ 898
Number of Securities | security	1,074	103
U.S. Government-sponsored mortgage-backed securities
Fair Value
Less than 12 Months	$ 206,559	$ 427,687
12 Months or Longer	312,109	8,324
Total	518,668	436,011
Gross Unrealized Losses
Less than 12 Months	23,141	10,791
12 Months or Longer	85,654	397
Total	$ 108,795	$ 11,188
Number of Securities | security	176	48
Corporate obligations
Fair Value
Less than 12 Months	$ 12,363	$ 992
12 Months or Longer	0	0
Total	12,363	992
Gross Unrealized Losses
Less than 12 Months	642	8
12 Months or Longer	0	0
Total	$ 642	$ 8
Number of Securities | security	10	1