Note 5 - Loans - Aging of Loan Portfolio (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Loans held for investment	$ 21,195,861	$ 20,147,202
Recorded investment	87,278	112,363
Financial Asset, 30 to 59 Days Past Due [Member]
Loans held for investment	23,157	50,063
Financial Asset, 60 to 89 Days Past Due [Member]
Loans held for investment	46,119	18,491
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans held for investment	4,994	1,000
Financial Asset, Past Due [Member]
Loans held for investment	161,548	181,917
Recorded investment	87,278	112,363
Financial Asset, Not Past Due [Member]
Loans held for investment	21,034,313	19,965,285
Commercial Portfolio Segment [Member]
Loans held for investment	3,945,390	3,184,556
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans held for investment	19,530	13,561
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans held for investment	15,565	1,376
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans held for investment	4,994	0
Commercial Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans held for investment	47,277	36,435
Recorded investment	7,188	21,498
Commercial Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans held for investment	3,898,113	3,148,121
Real Estate Construction Portfolio Segment [Member]
Loans held for investment	265,880	337,550
Real Estate Construction Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans held for investment	0	0
Real Estate Construction Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans held for investment	0	0
Real Estate Construction Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans held for investment	0	0
Real Estate Construction Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans held for investment	0	0
Recorded investment	0	0
Real Estate Construction Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans held for investment	265,880	337,550
Commercial Real Estate Portfolio Segment [Member]
Loans held for investment	10,844,794	10,564,744
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans held for investment	3,627	5,062
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans held for investment	12,939	6,254
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans held for investment	0	1,000
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans held for investment	63,812	71,827
Recorded investment	47,246	59,511
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans held for investment	10,780,982	10,492,917
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans held for investment	6,133,247	6,058,538
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans held for investment	0	31,440
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans held for investment	17,615	10,861
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans held for investment	0	0
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans held for investment	50,459	73,655
Recorded investment	32,844	31,354
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans held for investment	6,082,788	5,984,883
Installment and Other Loans [Member ]
Loans held for investment	6,550	1,814
Installment and Other Loans [Member ] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans held for investment	0	0
Installment and Other Loans [Member ] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans held for investment	0	0
Installment and Other Loans [Member ] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans held for investment	0	0
Installment and Other Loans [Member ] | Financial Asset, Past Due [Member]
Loans held for investment	0	0
Recorded investment	0	0
Installment and Other Loans [Member ] | Financial Asset, Not Past Due [Member]
Loans held for investment	$ 6,550	$ 1,814