Note 7 - Investment Securities (Tables)

9 Months Ended

Sep. 30, 2015

Investments, Debt and Equity Securities [Abstract]

Schedule of Available-for-sale Securities Reconciliation [Table Text Block]

	September 30, 2015
			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
	(In thousands)
Securities Available-for-Sale
U.S. treasury securities	$	284,603	$	388	$	-	$	284,991
Mortgage-backed securities		1,005,527		1,066		2,195		1,004,398
Collateralized mortgage obligations		67		-		29		38
Corporate debt securities		74,952		370		1,492		73,830
Mutual funds		6,000		-		101		5,899
Preferred stock of government sponsored entities		2,811		1,706		-		4,517
Other equity securities		4,128		3,403		325		7,206
Total	$	1,378,088	$	6,933	$	4,142	$	1,380,879

	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	$	184,935	$	185,127
Due after one year through five years		136,610		137,407
Due after five years through ten years		45,546		44,172
Due after ten years (1)		1,010,997		1,014,173
Total	$	1,378,088	$	1,380,879

Schedule of Unrealized Loss on Investments [Table Text Block]

	September 30, 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	$	703,710	$	2,194	$	7	$	1	$	703,717	$	2,195
Collateralized mortgage obligations		-		-		38		29		38		29
Corporate debt securities		9,950		50		43,558		1,442		53,508		1,492
Mutual funds		-		-		5,899		101		5,899		101
Other equity securities		175		325		-		-		175		325
Total	$	713,835	$	2,569	$	49,502	$	1,573	$	763,337	$	4,142

	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