Fair Value - Assets and liabilities measured at fair value on a recurring basis (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Assets
Derivative financial instruments	$ 666,600	$ 408,800
Trading securities	88,088	77,689
Securities available for sale	5,666,008	5,193,478
SBA servicing assets	6,400
Liabilities
Derivative financial instruments	666,500	408,800
U.S. Treasuries
Assets
Securities available for sale	316,458
U.S. Government agencies
Assets
Trading securities	13,428	5,154
Securities available for sale	203,087	97,117
Residential mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Trading securities	28,079	6,853
Securities available for sale	1,860,009	1,831,039
Commercial mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Trading securities	18,570	29,667
Securities available for sale	1,065,822	1,207,241
State and municipal obligations
Assets
Trading securities	9,357	20,798
Securities available for sale	1,068,558	812,689
Corporate securities.
Assets
Securities available for sale	29,608	18,734
Significant Other Observable Inputs (Level 2)
Assets
Loans held for sale	73,880	191,723
Trading securities	88,088	77,689
Significant Unobservable Inputs (Level 3)
Assets
Mortgage servicing rights	87,463	65,620
SBA servicing assets	6,449
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	668,324	414,742
Loans held for sale	73,880	191,723
Trading securities	88,088	77,689
Securities available for sale	5,666,008	5,193,478
Mortgage servicing rights	87,463	65,620
SBA servicing assets	6,449
Fair value of Assets, Total	6,590,212	5,943,252
Liabilities
Derivative financial instruments	666,802	410,137
Recurring basis | U.S. Treasuries
Assets
Securities available for sale	316,458
Recurring basis | U.S. Government agencies
Assets
Securities available for sale	203,087	97,117
Recurring basis | Residential mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Securities available for sale	1,860,009	1,831,039
Recurring basis | Residential Collateralized Mortgage-Obligations Issued By U.S. Government Agencies Or Sponsored Enterprises [Member]
Assets
Securities available for sale	667,514	725,995
Recurring basis | Commercial mortgage-backed securities issued by U.S. government agencies or sponsored enterprises
Assets
Securities available for sale	1,065,822	1,207,241
Recurring basis | State and municipal obligations
Assets
Securities available for sale	1,068,558	812,689
Recurring basis | Mortgage-backed securities
Assets
Securities available for sale	454,952	500,663
Recurring basis | Corporate securities.
Assets
Securities available for sale	29,608	18,734
Recurring basis | Significant Other Observable Inputs (Level 2)
Assets
Derivative financial instruments	668,324	414,742
Loans held for sale	73,880	191,723
Trading securities	88,088	77,689
Securities available for sale	5,666,008	5,193,478
Fair value of Assets, Total	6,496,300	5,877,632
Liabilities
Derivative financial instruments	666,802	410,137
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. Treasuries
Assets
Securities available for sale	316,458
Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. Government agencies
Assets
Securities available for sale	203,087	97,117
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	1,860,009	1,831,039
Recurring basis | Significant Other Observable Inputs (Level 2) | Residential Collateralized Mortgage-Obligations Issued By U.S. Government Agencies Or Sponsored Enterprises [Member]
Assets
Securities available for sale	667,514	725,995
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	1,065,822	1,207,241
Recurring basis | Significant Other Observable Inputs (Level 2) | State and municipal obligations
Assets
Securities available for sale	1,068,558	812,689
Recurring basis | Significant Other Observable Inputs (Level 2) | Mortgage-backed securities
Assets
Securities available for sale	454,952	500,663
Recurring basis | Significant Other Observable Inputs (Level 2) | Corporate securities.
Assets
Securities available for sale	29,608	18,734
Recurring basis | Significant Unobservable Inputs (Level 3)
Assets
Mortgage servicing rights	87,463	65,620
SBA servicing assets	6,449
Fair value of Assets, Total	93,912	$ 65,620
Changes in fair value of assets
Fair value of assets at the beginning of the period	65,620
Servicing assets that resulted from transfers of financial assets	11,751
Changes in fair value assets due to valuation inputs or assumptions	15,613
Changes in fair value due to decay	(5,521)
Fair value of assets at the end of the period	87,463
Unrealized losses included in accumulated other comprehensive income related to Level 3 financial assets and liabilities	$ 0