Note 6 - Investment Securities (Tables)

3 Months Ended

Mar. 31, 2015

Investments, Debt and Equity Securities [Abstract]

Schedule of Amortized Cost Gross Unrealized Gains Gross Unrealized Losses and Fair Values of Investment [Table Text Block]

	March 31, 2015
			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
	(In thousands)
Securities Available-for-Sale
U.S. treasury securities	$	349,830	$	353	$	-	$	350,183
Mortgage-backed securities		756,758		3,904		333		760,329
Collateralized mortgage obligations		74		-		32		42
Corporate debt securities		74,946		730		1,165		74,511
Mutual funds		6,000		-		79		5,921
Preferred stock of government sponsored entities		6,686		844		3,584		3,946
Other equity securities		3,628		5,125		3		8,750
Total	$	1,197,922	$	10,956	$	5,196	$	1,203,682

	December 31, 2014
			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
	(In thousands)
Securities Available-for-Sale
U.S. treasury securities	$	664,206	$	63	$	265	$	664,004
Mortgage-backed securities		549,296		1,393		6,386		544,303
Collateralized mortgage obligations		79		-		34		45
Corporate debt securities		94,943		776		1,247		94,472
Mutual funds		6,000		-		134		5,866
Preferred stock of government sponsored entities		6,276		681		3,733		3,224
Other equity securities		3,608		3,413		-		7,021
Total	$	1,324,408	$	6,326	$	11,799	$	1,318,935

Investments Classified by Contractual Maturity Date [Table Text Block]

	Securities Available-For-Sale
	Amortized cost		Fair value
	(In thousands)
Due in one year or less	$	174,987	$	175,062
Due after one year through five years		194,247		195,198
Due after five years through ten years		65,595		65,057
Due after ten years (1)		763,093		768,365
Total	$	1,197,922	$	1,203,682

Schedule of Unrealized Loss on Investments [Table Text Block]

	March 31, 2015
	Temporarily impaired securities
	Less than 12 months				12 months or longer				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
	(Dollars in thousands)
Securities Available-for-Sale
Mortgage-backed securities	$	145,297	$	332	$	7	$	1	$	145,304	$	333
Collateralized mortgage obligations		-		-		41		32		41		32
Corporate debt securities		-		-		43,835		1,165		43,835		1,165
Mutual funds		-		-		5,921		79		5,921		79
Preferred stock of government sponsored entities		2,597		3,584		-		-		2,597		3,584
Other equity securities		17		3		-		-		17		3
Total	$	147,911	$	3,919	$	49,804	$	1,277	$	197,715	$	5,196

	December 31, 2014
	Temporarily impaired securities
	Less than 12 months				12 months or longer				Total
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
	Value		Losses		Value		Losses		Value		Losses
	(Dollars in thousands)
Securities Available-for-Sale
U.S. treasury securities	$	374,153	$	265	$	-	$	-	$	374,153	$	265
Mortgage-backed securities		-		-		425,090		6,386		425,090		6,386
Collateralized mortgage obligations		-		-		45		34		45		34
Corporate debt securities		-		-		63,753		1,247		63,753		1,247
Mutual funds		-		-		5,866		134		5,866		134
Preferred stock of government sponsored entities		2,448		3,733		-		-		2,448		3,733
Total	$	376,601	$	3,998	$	494,754	$	7,801	$	871,355	$	11,799