Note 8 - Loans - Loan Held for Investment by Loan Portfolio Segments, Internal Risk Ratings and Vintage Year (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Loans originated in current year	$ 620,981		$ 3,724,618
Loans originated year prior	3,676,808		3,581,730
Loans originated three years prior	3,500,408		3,052,314
Loans originated four years prior	2,939,149		1,588,314
Loans originated five years prior	1,530,950		1,686,965
Total, Loans Amortized Cost Basis by Origination Year Prior	4,949,750		3,571,544
Total, Revolving Loans	2,174,209		2,306,710
Total, Revolving Converted to Term Loans	25,404		25,225
Total loans	19,417,659		19,537,420
Loans originated in current year, write offs	0		0
Loans originated year prior, write offs	193		992
Loans originated three years prior, write offs	342		1,520
Loans originated four years prior, write offs	196		384
Loans originated five years prior, write offs	98		4,641
Total, Loans Amortized Cost Basis by Origination Year Prior, Write Offs	291		14,429
Total, Revolving Loans Write Offs	1,070		1,520
Total, Revolving Converted to Term Loans, Write Offs	3		0
YTD gross write-offs	2,193	$ 7,907	23,486
Total loans	19,417,659		19,537,420
Commercial Portfolio Segment [Member]
Loans originated in current year	112,388		387,945
Loans originated year prior	369,374		329,467
Loans originated three years prior	298,536		345,104
Loans originated four years prior	311,032		122,567
Loans originated five years prior	96,912		76,044
Total, Loans Amortized Cost Basis by Origination Year Prior	148,330		141,937
Total, Revolving Loans	1,782,584		1,890,712
Total, Revolving Converted to Term Loans	8,858		8,424
Total loans	3,128,014		3,302,200
Loans originated in current year, write offs	0		0
Loans originated year prior, write offs	193		977
Loans originated three years prior, write offs	342		1,312
Loans originated four years prior, write offs	196		384
Loans originated five years prior, write offs	98		3,672
Total, Loans Amortized Cost Basis by Origination Year Prior, Write Offs	40		6,044
Total, Revolving Loans Write Offs	1,070		1,520
Total, Revolving Converted to Term Loans, Write Offs	0		0
YTD gross write-offs	1,939	3,911	13,909
Total loans	3,128,014		3,302,200
Commercial Portfolio Segment [Member] | Pass [Member]
Loans originated in current year	112,388		381,705
Loans originated year prior	363,390		323,939
Loans originated three years prior	288,235		326,650
Loans originated four years prior	285,412		96,725
Loans originated five years prior	71,446		75,281
Total, Loans Amortized Cost Basis by Origination Year Prior	141,867		136,162
Total, Revolving Loans	1,670,791		1,775,162
Total, Revolving Converted to Term Loans	8,632		8,308
Total loans	2,942,161		3,123,932
Total loans	2,942,161		3,123,932
Commercial Portfolio Segment [Member] | Special Mention [Member]
Loans originated in current year	0		4,488
Loans originated year prior	0		4,875
Loans originated three years prior	9,791		8,559
Loans originated four years prior	15,092		23,380
Loans originated five years prior	23,013		0
Total, Loans Amortized Cost Basis by Origination Year Prior	0		0
Total, Revolving Loans	63,531		75,419
Total, Revolving Converted to Term Loans	50		0
Total loans	111,477		116,721
Total loans	111,477		116,721
Commercial Portfolio Segment [Member] | Substandard [Member]
Loans originated in current year	0		1,752
Loans originated year prior	5,984		653
Loans originated three years prior	510		9,895
Loans originated four years prior	10,528		2,462
Loans originated five years prior	2,453		763
Total, Loans Amortized Cost Basis by Origination Year Prior	6,463		5,775
Total, Revolving Loans	48,262		40,131
Total, Revolving Converted to Term Loans	176		116
Total loans	74,376		61,547
Total loans	74,376		61,547
Real Estate Construction Portfolio Segment [Member]
Loans originated in current year	0		31,461
Loans originated year prior	37,572		131,984
Loans originated three years prior	138,347		165,684
Loans originated four years prior	124,103		44,850
Loans originated five years prior	45,013		21,034
Total, Loans Amortized Cost Basis by Origination Year Prior	36,611		26,129
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	381,646		421,142
Loans originated in current year, write offs	0		0
Loans originated year prior, write offs	0		0
Loans originated three years prior, write offs	0		0
Loans originated four years prior, write offs	0		0
Loans originated five years prior, write offs	0		0
Total, Loans Amortized Cost Basis by Origination Year Prior, Write Offs	0		4,221
Total, Revolving Loans Write Offs	0		0
Total, Revolving Converted to Term Loans, Write Offs	0		0
YTD gross write-offs	0	(0)	4,221
Total loans	381,646		421,142
Real Estate Construction Portfolio Segment [Member] | Pass [Member]
Loans originated in current year	0		29,550
Loans originated year prior	34,582		131,984
Loans originated three years prior	138,347		153,977
Loans originated four years prior	124,103		19,461
Loans originated five years prior	19,592		13,298
Total, Loans Amortized Cost Basis by Origination Year Prior	13,613		3,131
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	330,237		351,401
Total loans	330,237		351,401
Real Estate Construction Portfolio Segment [Member] | Special Mention [Member]
Loans originated in current year	0		1,911
Loans originated year prior	2,990		0
Loans originated three years prior	0		11,707
Loans originated four years prior	0		25,389
Loans originated five years prior	25,421		0
Total, Loans Amortized Cost Basis by Origination Year Prior	0		22,998
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	28,411		62,005
Total loans	28,411		62,005
Real Estate Construction Portfolio Segment [Member] | Substandard [Member]
Loans originated in current year	0		0
Loans originated year prior	0		0
Loans originated three years prior	0		0
Loans originated four years prior	0		0
Loans originated five years prior	0		7,736
Total, Loans Amortized Cost Basis by Origination Year Prior	22,998		0
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	22,998		7,736
Total loans	22,998		7,736
Commercial Real Estate Portfolio Segment [Member]
Loans originated in current year	326,752		2,159,093
Loans originated year prior	2,156,098		1,990,019
Loans originated three years prior	1,956,654		1,635,585
Loans originated four years prior	1,617,736		893,972
Loans originated five years prior	878,998		1,047,548
Total, Loans Amortized Cost Basis by Origination Year Prior	2,715,995		1,809,430
Total, Revolving Loans	162,079		185,985
Total, Revolving Converted to Term Loans	0		0
Total loans	9,814,312		9,721,632
Loans originated in current year, write offs	0		0
Loans originated year prior, write offs	0		0
Loans originated three years prior, write offs	0		208
Loans originated four years prior, write offs	0		0
Loans originated five years prior, write offs	0		969
Total, Loans Amortized Cost Basis by Origination Year Prior, Write Offs	251		4,164
Total, Revolving Loans Write Offs	0		0
Total, Revolving Converted to Term Loans, Write Offs	0		0
YTD gross write-offs	251	3,990	5,341
Total loans	9,814,312		9,721,632
Commercial Real Estate Portfolio Segment [Member] | Pass [Member]
Loans originated in current year	326,264		2,121,489
Loans originated year prior	2,121,324		1,959,239
Loans originated three years prior	1,926,019		1,585,010
Loans originated four years prior	1,565,519		887,508
Loans originated five years prior	874,626		1,019,952
Total, Loans Amortized Cost Basis by Origination Year Prior	2,605,759		1,726,015
Total, Revolving Loans	160,035		184,601
Total, Revolving Converted to Term Loans	0		0
Total loans	9,579,546		9,483,814
Total loans	9,579,546		9,483,814
Commercial Real Estate Portfolio Segment [Member] | Special Mention [Member]
Loans originated in current year	488		37,604
Loans originated year prior	23,587		18,910
Loans originated three years prior	16,213		38,405
Loans originated four years prior	40,453		3,499
Loans originated five years prior	1,407		10,303
Total, Loans Amortized Cost Basis by Origination Year Prior	19,526		17,210
Total, Revolving Loans	1,380		1,384
Total, Revolving Converted to Term Loans	0		0
Total loans	103,054		127,315
Total loans	103,054		127,315
Commercial Real Estate Portfolio Segment [Member] | Substandard [Member]
Loans originated in current year	0		0
Loans originated year prior	11,187		11,870
Loans originated three years prior	14,422		12,170
Loans originated four years prior	11,764		2,965
Loans originated five years prior	2,965		17,293
Total, Loans Amortized Cost Basis by Origination Year Prior	90,710		66,205
Total, Revolving Loans	664		0
Total, Revolving Converted to Term Loans	0		0
Total loans	131,712		110,503
Total loans	131,712		110,503
Residential Portfolio Segment [Member]
Loans originated in current year	180,962		1,141,005
Loans originated year prior	1,109,737		1,129,178
Loans originated three years prior	1,106,613		905,938
Loans originated four years prior	886,276		526,925
Loans originated five years prior	510,027		542,339
Total, Loans Amortized Cost Basis by Origination Year Prior	2,048,814		1,594,048
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	5,842,429		5,839,433
Loans originated in current year, write offs	0		0
Loans originated year prior, write offs	0		0
Loans originated three years prior, write offs	0		0
Loans originated four years prior, write offs	0		0
Loans originated five years prior, write offs	0		0
Total, Loans Amortized Cost Basis by Origination Year Prior, Write Offs	0		0
Total, Revolving Loans Write Offs	0		0
Total, Revolving Converted to Term Loans, Write Offs	0		0
YTD gross write-offs	0		0
Total loans	5,842,429		5,839,433
Residential Portfolio Segment [Member] | Pass [Member]
Loans originated in current year	180,962		1,140,998
Loans originated year prior	1,109,711		1,128,526
Loans originated three years prior	1,106,601		902,613
Loans originated four years prior	884,987		524,315
Loans originated five years prior	506,331		541,005
Total, Loans Amortized Cost Basis by Origination Year Prior	2,034,462		1,583,118
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	5,823,054		5,820,575
Total loans	5,823,054		5,820,575
Residential Portfolio Segment [Member] | Special Mention [Member]
Loans originated in current year	0		0
Loans originated year prior	0		0
Loans originated three years prior	0		0
Loans originated four years prior	0		33
Loans originated five years prior	340		0
Total, Loans Amortized Cost Basis by Origination Year Prior	6,101		1,619
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	6,441		1,652
Total loans	6,441		1,652
Residential Portfolio Segment [Member] | Substandard [Member]
Loans originated in current year	0		7
Loans originated year prior	26		652
Loans originated three years prior	12		3,325
Loans originated four years prior	1,289		2,577
Loans originated five years prior	3,356		1,334
Total, Loans Amortized Cost Basis by Origination Year Prior	8,251		9,311
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	12,934		17,206
Total loans	12,934		17,206
Equity Lines Portfolio Segment [Member]
Loans originated in current year	0		0
Loans originated year prior	0		101
Loans originated three years prior	92		0
Loans originated four years prior	0		0
Loans originated five years prior	0		0
Total, Loans Amortized Cost Basis by Origination Year Prior	0		0
Total, Revolving Loans	229,546		230,013
Total, Revolving Converted to Term Loans	16,546		16,801
Total loans	246,184		246,915
Loans originated in current year, write offs	0		0
Loans originated year prior, write offs	0		0
Loans originated three years prior, write offs	0		0
Loans originated four years prior, write offs	0		0
Loans originated five years prior, write offs	0		0
Total, Loans Amortized Cost Basis by Origination Year Prior, Write Offs	0		0
Total, Revolving Loans Write Offs	0		0
Total, Revolving Converted to Term Loans, Write Offs	3		0
YTD gross write-offs	3		0
Total loans	246,184		246,915
Equity Lines Portfolio Segment [Member] | Pass [Member]
Loans originated in current year	0		0
Loans originated year prior	0		98
Loans originated three years prior	92		0
Loans originated four years prior	0		0
Loans originated five years prior	0		0
Total, Loans Amortized Cost Basis by Origination Year Prior	0		0
Total, Revolving Loans	227,752		227,502
Total, Revolving Converted to Term Loans	16,374		16,628
Total loans	244,218		244,228
Total loans	244,218		244,228
Equity Lines Portfolio Segment [Member] | Special Mention [Member]
Loans originated in current year			0
Loans originated year prior			3
Loans originated three years prior			0
Loans originated four years prior			0
Loans originated five years prior			0
Total, Loans Amortized Cost Basis by Origination Year Prior			0
Total, Revolving Loans			0
Total, Revolving Converted to Term Loans			0
Total loans			3
Total loans			3
Equity Lines Portfolio Segment [Member] | Substandard [Member]
Loans originated in current year	0		0
Loans originated year prior	0		0
Loans originated three years prior	0		0
Loans originated four years prior	0		0
Loans originated five years prior	0		0
Total, Loans Amortized Cost Basis by Origination Year Prior	0		0
Total, Revolving Loans	1,794		2,511
Total, Revolving Converted to Term Loans	172		173
Total loans	1,966		2,684
Total loans	1,966		2,684
Installment and Other Loans [Member ]
Loans originated in current year	879		5,114
Loans originated year prior	4,027		981
Loans originated three years prior	166		3
Loans originated four years prior	2		0
Loans originated five years prior	0		0
Total, Loans Amortized Cost Basis by Origination Year Prior	0		0
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	5,074		6,098
Loans originated in current year, write offs	0		0
Loans originated year prior, write offs	0		15
Loans originated three years prior, write offs	0		0
Loans originated four years prior, write offs	0		0
Loans originated five years prior, write offs	0		0
Total, Loans Amortized Cost Basis by Origination Year Prior, Write Offs	0		0
Total, Revolving Loans Write Offs	0		0
Total, Revolving Converted to Term Loans, Write Offs	0		0
YTD gross write-offs	0	$ 6	15
Total loans	5,074		6,098
Installment and Other Loans [Member ] | Pass [Member]
Loans originated in current year	879		5,114
Loans originated year prior	4,027		981
Loans originated three years prior	166		3
Loans originated four years prior	2		0
Loans originated five years prior	0		0
Total, Loans Amortized Cost Basis by Origination Year Prior	0		0
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	5,074		6,098
Total loans	$ 5,074		$ 6,098