Note 9 - 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, 2023	Mar. 31, 2022	Dec. 31, 2022
Loans originated in current year	$ 725,864		$ 3,943,040
Loans originated year prior	3,890,115		3,489,846
Loans originated three years prior	3,413,288		1,905,136
Loans originated four years prior	1,846,427		1,908,992
Loans originated five years prior	1,854,485		1,530,238
Total, Loans Amortized Cost Basis by Origination Year Prior	4,392,896		3,138,606
Total, Revolving Loans	2,161,920		2,303,152
Total, Revolving Converted to Term Loans	26,472		28,373
Total loans	18,311,467		18,247,383
Loans originated in current year, write offs	0		211
Loans originated year prior, write offs	170		587
Loans originated three years prior, write offs	968		120
Loans originated four years prior, write offs	145		71
Loans originated five years prior, write offs	2,053		3,877
Total, Loans Amortized Cost Basis by Origination Year Prior, Write Offs	4,560		360
Total, Revolving Loans Write Offs	11		264
Total, Revolving Converted to Term Loans, Write Offs	0		0
YTD gross writeoffs	7,907	$ 221	5,490
Total loans	18,311,467		18,247,383
Commercial Portfolio Segment [Member]
Loans originated in current year	62,760		489,985
Loans originated year prior	464,215		464,093
Loans originated three years prior	452,495		183,386
Loans originated four years prior	164,011		125,786
Loans originated five years prior	102,406		113,155
Total, Loans Amortized Cost Basis by Origination Year Prior	202,772		117,988
Total, Revolving Loans	1,698,264		1,816,937
Total, Revolving Converted to Term Loans	6,051		6,693
Total loans	3,152,974		3,318,023
Loans originated in current year, write offs	0		96
Loans originated year prior, write offs	164		587
Loans originated three years prior, write offs	760		120
Loans originated four years prior, write offs	145		71
Loans originated five years prior, write offs	2,053		1,786
Total, Loans Amortized Cost Basis by Origination Year Prior, Write Offs	778		360
Total, Revolving Loans Write Offs	11		202
Total, Revolving Converted to Term Loans, Write Offs	0		0
YTD gross writeoffs	3,911	221	3,222
Total loans	3,152,974		3,318,023
Commercial Portfolio Segment [Member] | Pass [Member]
Loans originated in current year	62,760		488,748
Loans originated year prior	462,944		446,647
Loans originated three years prior	436,143		180,226
Loans originated four years prior	161,289		119,355
Loans originated five years prior	99,233		107,896
Total, Loans Amortized Cost Basis by Origination Year Prior	191,552		106,649
Total, Revolving Loans	1,631,086		1,753,509
Total, Revolving Converted to Term Loans	5,231		6,560
Total loans	3,050,238		3,209,590
Total loans	3,050,238		3,209,590
Commercial Portfolio Segment [Member] | Special Mention [Member]
Loans originated in current year	0		1,212
Loans originated year prior	1,212		4,696
Loans originated three years prior	3,822		2,818
Loans originated four years prior	2,437		68
Loans originated five years prior	0		308
Total, Loans Amortized Cost Basis by Origination Year Prior	3,540		4,354
Total, Revolving Loans	46,123		41,110
Total, Revolving Converted to Term Loans	0		0
Total loans	57,134		54,566
Total loans	57,134		54,566
Commercial Portfolio Segment [Member] | Substandard [Member]
Loans originated in current year	0		25
Loans originated year prior	59		12,750
Loans originated three years prior	12,530		342
Loans originated four years prior	285		4,859
Loans originated five years prior	3,173		2,766
Total, Loans Amortized Cost Basis by Origination Year Prior	6,274		6,985
Total, Revolving Loans	20,823		22,084
Total, Revolving Converted to Term Loans	820		133
Total loans	43,964		49,944
Total loans	43,964		49,944
Commercial Portfolio Segment [Member] | Doubtful [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		1,504
Loans originated five years prior	0		2,185
Total, Loans Amortized Cost Basis by Origination Year Prior	1,406		0
Total, Revolving Loans	232		234
Total, Revolving Converted to Term Loans	0		0
Total loans	1,638		3,923
Total loans	1,638		3,923
Real Estate Construction Portfolio Segment [Member]
Loans originated in current year	11,190		99,798
Loans originated year prior	114,805		264,557
Loans originated three years prior	250,438		122,761
Loans originated four years prior	112,823		33,858
Loans originated five years prior	32,068		35,321
Total, Loans Amortized Cost Basis by Origination Year Prior	35,336		0
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	556,660		556,295
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 writeoffs	0	(0)	0
Total loans	556,660		556,295
Real Estate Construction Portfolio Segment [Member] | Pass [Member]
Loans originated in current year	11,190		99,798
Loans originated year prior	114,805		264,197
Loans originated three years prior	249,947		113,312
Loans originated four years prior	112,823		20,479
Loans originated five years prior	18,429		3,067
Total, Loans Amortized Cost Basis by Origination Year Prior	3,072		0
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	510,266		500,853
Total loans	510,266		500,853
Real Estate Construction Portfolio Segment [Member] | Special Mention [Member]
Loans originated in current year	0		0
Loans originated year prior	0		360
Loans originated three years prior	491		9,449
Loans originated four years prior	0		11,643
Loans originated five years prior	11,903		22,945
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	35,392		44,397
Total loans	35,392		44,397
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		1,736
Loans originated five years prior	1,736		9,309
Total, Loans Amortized Cost Basis by Origination Year Prior	9,266		0
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	11,002		11,045
Total loans	11,002		11,045
Commercial Real Estate Portfolio Segment [Member]
Loans originated in current year	387,087		2,122,120
Loans originated year prior	2,111,921		1,793,483
Loans originated three years prior	1,756,600		1,015,938
Loans originated four years prior	998,326		1,146,596
Loans originated five years prior	1,131,459		961,646
Total, Loans Amortized Cost Basis by Origination Year Prior	2,341,376		1,566,608
Total, Revolving Loans	184,470		182,347
Total, Revolving Converted to Term Loans	0		0
Total loans	8,911,239		8,788,738
Loans originated in current year, write offs	0		0
Loans originated year prior, write offs	0		0
Loans originated three years prior, write offs	208		0
Loans originated four years prior, write offs	0		0
Loans originated five years prior, write offs	0		2,091
Total, Loans Amortized Cost Basis by Origination Year Prior, Write Offs	3,782		0
Total, Revolving Loans Write Offs	0		0
Total, Revolving Converted to Term Loans, Write Offs	0		0
YTD gross writeoffs	3,990	(0)	2,091
Total loans	8,911,239		8,788,738
Commercial Real Estate Portfolio Segment [Member] | Pass [Member]
Loans originated in current year	387,087		2,087,650
Loans originated year prior	2,077,494		1,728,607
Loans originated three years prior	1,715,118		975,953
Loans originated four years prior	958,330		1,094,505
Loans originated five years prior	1,090,519		908,748
Total, Loans Amortized Cost Basis by Origination Year Prior	2,176,822		1,420,982
Total, Revolving Loans	181,831		178,116
Total, Revolving Converted to Term Loans	0		0
Total loans	8,587,201		8,394,561
Total loans	8,587,201		8,394,561
Commercial Real Estate Portfolio Segment [Member] | Special Mention [Member]
Loans originated in current year	0		22,150
Loans originated year prior	22,150		57,015
Loans originated three years prior	29,121		25,593
Loans originated four years prior	25,604		32,119
Loans originated five years prior	21,038		17,999
Total, Loans Amortized Cost Basis by Origination Year Prior	57,120		63,782
Total, Revolving Loans	0		1,600
Total, Revolving Converted to Term Loans	0		0
Total loans	155,033		220,258
Total loans	155,033		220,258
Commercial Real Estate Portfolio Segment [Member] | Substandard [Member]
Loans originated in current year	0		12,320
Loans originated year prior	12,277		7,861
Loans originated three years prior	12,361		14,392
Loans originated four years prior	14,392		19,972
Loans originated five years prior	19,902		34,899
Total, Loans Amortized Cost Basis by Origination Year Prior	107,434		81,844
Total, Revolving Loans	2,639		2,631
Total, Revolving Converted to Term Loans	0		0
Total loans	169,005		173,919
Total loans	169,005		173,919
Residential Portfolio Segment [Member]
Loans originated in current year	264,586		1,228,597
Loans originated year prior	1,196,474		965,561
Loans originated three years prior	950,977		583,051
Loans originated four years prior	571,267		602,752
Loans originated five years prior	588,552		420,116
Total, Loans Amortized Cost Basis by Origination Year Prior	1,813,412		1,454,010
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	5,385,268		5,254,087
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 writeoffs	0		0
Total loans	5,385,268		5,254,087
Residential Portfolio Segment [Member] | Pass [Member]
Loans originated in current year	264,586		1,228,391
Loans originated year prior	1,195,811		964,799
Loans originated three years prior	950,229		580,990
Loans originated four years prior	570,344		600,786
Loans originated five years prior	586,635		417,565
Total, Loans Amortized Cost Basis by Origination Year Prior	1,800,951		1,444,320
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	5,368,556		5,236,851
Total loans	5,368,556		5,236,851
Residential Portfolio Segment [Member] | Special Mention [Member]
Loans originated in current year	0		0
Loans originated year prior	459		0
Loans originated three years prior	0		33
Loans originated four years prior	489		0
Loans originated five years prior	678		752
Total, Loans Amortized Cost Basis by Origination Year Prior	2,275		905
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	3,901		1,690
Total loans	3,901		1,690
Residential Portfolio Segment [Member] | Substandard [Member]
Loans originated in current year	0		206
Loans originated year prior	204		762
Loans originated three years prior	748		2,028
Loans originated four years prior	434		1,966
Loans originated five years prior	1,239		1,799
Total, Loans Amortized Cost Basis by Origination Year Prior	10,186		8,785
Total, Revolving Loans	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	12,811		15,546
Total loans	12,811		15,546
Equity Lines Portfolio Segment [Member]
Loans originated in current year	0		748
Loans originated year prior	127		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	279,186		303,868
Total, Revolving Converted to Term Loans	20,421		21,680
Total loans	299,734		326,296
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 writeoffs	0		0
Total loans	299,734		326,296
Equity Lines Portfolio Segment [Member] | Pass [Member]
Loans originated in current year	0		731
Loans originated year prior	127		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	277,548		302,825
Total, Revolving Converted to Term Loans	20,217		21,460
Total loans	297,892		325,016
Total loans	297,892		325,016
Equity Lines Portfolio Segment [Member] | Special Mention [Member]
Loans originated in current year	0		5
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	11		0
Total, Revolving Converted to Term Loans	0		0
Total loans	11		5
Total loans	11		5
Equity Lines Portfolio Segment [Member] | Substandard [Member]
Loans originated in current year	0		12
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	1,627		1,043
Total, Revolving Converted to Term Loans	204		220
Total loans	1,831		1,275
Total loans	1,831		1,275
Installment and Other Loans [Member ]
Loans originated in current year	241		1,792
Loans originated year prior	2,573		2,152
Loans originated three years prior	2,778		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	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	5,592		3,944
Loans originated in current year, write offs	0		115
Loans originated year prior, write offs	6		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		62
Total, Revolving Converted to Term Loans, Write Offs	0		0
YTD gross writeoffs	6	$ (0)	177
Total loans	5,592		3,944
Installment and Other Loans [Member ] | Pass [Member]
Loans originated in current year	241		1,792
Loans originated year prior	2,573		2,152
Loans originated three years prior	2,778		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	0		0
Total, Revolving Converted to Term Loans	0		0
Total loans	5,592		3,944
Total loans	$ 5,592		$ 3,944