Note 3 - Investment Securities (Tables)

12 Months Ended

Dec. 31, 2015

Investments, Debt and Equity Securities [Abstract]

Investment [Table Text Block]

	Years Ended December 31
	2015									2014
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized (Losses)			Estimated Fair Value
Held-to-Maturity
U.S. Government agencies	$	237,139	$	582	$	(1,395	)	$	236,326	$	418,914	$	929	$	(4,055	)	$	415,788
Mortgage-backed securities		24,774		86		(290	)		24,570		29,743		56		(411	)		29,388
State and political subdivisions		440,676		9,138		(123	)		449,691		328,310		7,000		(573	)		334,737
Other securities		2,784		--		--			2,784		620		--		--			620
Total	$	705,373	$	9,806	$	(1,808	)	$	713,371	$	777,587	$	7,985	$	(5,039	)	$	780,533
Available-for-Sale
U.S. Treasury	$	4,000	$	--	$	(6	)	$	3,994	$	4,000	$	1	$	(9	)	$	3,992
U.S. Government agencies		121,017		118		(898	)		120,237		275,381		15		(2,580	)		272,816
Mortgage-backed securities		650,619		937		(4,130	)		647,426		1,579		--		(7	)		1,572
State and political subdivisions		9,762		112		--			9,874		6,536		7		(3	)		6,540
Other securities		40,394		420		(938	)		39,876		19,985		386		(8	)		20,363
Total	$	825,792	$	1,587	$	(5,972	)	$	821,407	$	307,481	$	409	$	(2,607	)	$	305,283

Schedule of Unrealized Loss on Investments [Table Text Block]

	Less Than 12 Months				12 Months or More				Total
(In thousands)	Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses		Estimated Fair Value		Gross Unrealized Losses
December 31, 2015
Held-to-Maturity
U.S. Government agencies	$	107,758	$	567	$	79,166	$	828	$	186,924	$	1,395
Mortgage-backed securities		7,958		94		8,144		196		16,102		290
State and political subdivisions		27,866		100		3,946		23		31,812		123
Total	$	143,582	$	761	$	91,256	$	1,047	$	234,838	$	1,808
Available-for-Sale
U.S. Treasury	$	3,994	$	6	$	--	$	--	$	3,994	$	6
U.S. Government agencies		62,473		317		46,023		581		108,496		898
Mortgage-backed securities		523,185		4,130		--		--		523,185		4,130
State and political subdivisions		281		--		--		--		281		--
Other securities		1,060		937		510		1		1,570		938
Total	$	590,993	$	5,390	$	46,533	$	582	$	637,526	$	5,972
December 31, 2014
Held-to-Maturity
U.S. Government agencies	$	265,591	$	2,500	$	84,398	$	1,555	$	349,989	$	4,055
Mortgage-backed securities		10,077		67		14,250		344		24,327		411
State and political subdivisions		57,607		444		8,976		129		66,583		573
Total	$	333,275	$	3,011	$	107,624	$	2,028	$	440,899	$	5,039
Available-for-Sale
U.S. Treasury	$	3,992	$	9	$	--	$	--	$	3,992	$	9
U.S. Government agencies		171,114		1,472		61,195		1,108		232,309		2,580
Mortgage-backed securities		1,542		7		--		--		1,542		7
State and political subdivisions		1,005		3		--		--		1,005		3
Other securities		764		8		--		--		764		8
Total	$	178,417	$	1,499	$	61,195	$	1,108	$	239,612	$	2,607

Investment Income [Table Text Block]

(In thousands)	2015		2014		2013
Taxable
Held-to-maturity	$	5,162	$	5,839	$	3,314
Available-for-sale		12,129		2,785		2,239
Non-taxable
Held-to-maturity		11,635		10,625		7,682
Available-for-sale		1,687		108		65
Total	$	30,613	$	19,357	$	13,300

Investments Classified by Contractual Maturity Date [Table Text Block]

	Held-to-Maturity				Available-for-Sale
(In thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair   Value
One year or less	$	28,739	$	28,807	$	28,543	$	28,512
After one through five years		315,065		314,557		88,911		88,048
After five through ten years		127,795		130,087		13,727		13,899
After ten years		209,000		215,350		5,363		5,412
Securities not due on a single maturity date		24,774		24,570		650,619		647,426
Other securities (no maturity)		--		--		38,629		38,110
Total	$	705,373	$	713,371	$	825,792	$	821,407