Fair Value - Assets and liabilities measured at fair value on a recurring basis (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Assets
Derivative financial instruments	$ 174,000	$ 169,000
Trading securities	66,188	31,321
Securities available for sale	4,598,400	4,784,388
SBA servicing asset	6,400	6,000
Liabilities
Derivative financial instruments	954,300,000	803,500,000
U.S. Treasuries
Assets
Securities available for sale	24,587	73,890
U.S. Government agencies
Assets
Trading securities	10,352	1,537
Securities available for sale	223,805	224,706
Residential mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Trading securities	11,383	14,461
Securities available for sale	1,492,423	1,558,306
Commercial mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Trading securities	8,467
Securities available for sale	1,012,217	1,024,170
State and municipal obligations
Assets
Trading securities	31,263	14,620
Securities available for sale	960,359	977,461
Small Business Administration loan-backed securities
Assets
Securities available for sale	350,043	371,686
Corporate securities.
Assets
Securities available for sale	26,854	26,747
Significant Other Observable Inputs (Level 2)
Assets
Loans held for sale	56,553	50,888
Trading securities	66,188	31,321
Significant Unobservable Inputs (Level 3)
Assets
Mortgage servicing rights	87,970	85,164
SBA servicing asset	6,367	5,952
Changes in fair value of assets
Changes in hierarchy classifications of Level 3 assets	0
Changes in hierarchy classifications of Level 3 liabilities	0
Recurring basis
Assets
Derivative financial instruments	176,784	172,939
Loans held for sale	56,553	50,888
Trading securities	66,188	31,321
Securities available for sale	4,598,400	4,784,388
Mortgage servicing rights	87,970	85,164
SBA servicing asset	6,367	5,952
Fair value of Assets, Total	4,992,262	5,130,652
Liabilities
Derivative financial instruments	954,788	804,486
Recurring basis | U.S. Treasuries
Assets
Securities available for sale	24,587	73,890
Recurring basis | U.S. Government agencies
Assets
Securities available for sale	223,805	224,706
Recurring basis | Residential mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Securities available for sale	1,492,423	1,558,306
Recurring basis | Residential Collateralized Mortgage-Obligations Issued By U.S. Government Agencies Or Sponsored Enterprises
Assets
Securities available for sale	508,112	527,422
Recurring basis | Commercial mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Securities available for sale	1,012,217	1,024,170
Recurring basis | State and municipal obligations
Assets
Securities available for sale	960,359	977,461
Recurring basis | Small Business Administration loan-backed securities
Assets
Securities available for sale	350,043	371,686
Recurring basis | Corporate securities.
Assets
Securities available for sale	26,854	26,747
Recurring basis | Significant Other Observable Inputs (Level 2)
Assets
Derivative financial instruments	176,784	172,939
Loans held for sale	56,553	50,888
Trading securities	66,188	31,321
Securities available for sale	4,598,400	4,784,388
Fair value of Assets, Total	4,897,925	5,039,536
Liabilities
Derivative financial instruments	954,788	804,486
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. Treasuries
Assets
Securities available for sale	24,587	73,890
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. Government agencies
Assets
Securities available for sale	223,805	224,706
Recurring basis | Significant Other Observable Inputs (Level 2) | Residential mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Securities available for sale	1,492,423	1,558,306
Recurring basis | Significant Other Observable Inputs (Level 2) | Residential Collateralized Mortgage-Obligations Issued By U.S. Government Agencies Or Sponsored Enterprises
Assets
Securities available for sale	508,112	527,422
Recurring basis | Significant Other Observable Inputs (Level 2) | Commercial mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Securities available for sale	1,012,217	1,024,170
Recurring basis | Significant Other Observable Inputs (Level 2) | State and municipal obligations
Assets
Securities available for sale	960,359	977,461
Recurring basis | Significant Other Observable Inputs (Level 2) | Small Business Administration loan-backed securities
Assets
Securities available for sale	350,043	371,686
Recurring basis | Significant Other Observable Inputs (Level 2) | Corporate securities.
Assets
Securities available for sale	26,854	26,747
Recurring basis | Significant Unobservable Inputs (Level 3)
Assets
Mortgage servicing rights	87,970	85,164
SBA servicing asset	6,367	5,952
Fair value of Assets, Total	$ 94,337	$ 91,116
Changes in fair value of assets
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Revenue from Contract with Customer, Excluding Assessed Tax
Unrealized losses included in accumulated other comprehensive (loss) income related to Level 3 financial assets and liabilities	$ 0
Recurring basis | Significant Unobservable Inputs (Level 3) | Mortgage Servicing Rights
Changes in fair value of assets
Fair value of assets at the beginning of the period	85,164
Servicing assets that resulted from transfers of financial assets	1,864
Changes in fair value assets due to valuation inputs or assumptions	2,384
Changes in fair value due to decay	(1,442)
Fair value of assets at the end of the period	87,970
Recurring basis | Significant Unobservable Inputs (Level 3) | SBA servicing asset
Changes in fair value of assets
Fair value of assets at the beginning of the period	5,952
Servicing assets that resulted from transfers of financial assets	581
Changes in fair value assets due to valuation inputs or assumptions	$ 198
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Revenue from Contract with Customer, Excluding Assessed Tax
Changes in fair value due to decay	$ (364)
Fair value of assets at the end of the period	$ 6,367