Note 4 - Investment Securities (Tables)

12 Months Ended

Dec. 31, 2014

Investments, Debt and Equity Securities [Abstract]

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

	As of 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 securities available-for-sale	$	1,324,408	$	6,326	$	11,799	$	1,318,935

	As of December 31, 2013
			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
	(In thousands)
Securities Available-for-Sale
U.S. treasury securities	$	460,095	$	99	$	1	$	460,193
Mortgage-backed securities		1,010,294		7,049		64,529		952,814
Collateralized mortgage obligations		5,929		231		54		6,106
Asset-backed securities		123		-		-		123
Corporate debt securities		154,955		298		4,949		150,304
Mutual funds		6,000		-		275		5,725
Preferred stock of government sponsored entities		569		10,834		-		11,403
Total securities available-for-sale	$	1,637,965	$	18,511	$	69,808	$	1,586,668

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	$	115,033	$	115,068
Due after one year through five years		569,853		570,371
Due after five years through ten years		85,654		85,097
Due after ten years (1)		553,868		548,399
Total	$	1,324,408	$	1,318,935

Schedule of Unrealized Loss on Investments [Table Text Block]

	As of December 31, 2014
	Temporarily Impaired Securities
	Less than 12 months						12 months or longer						Total
	Fair		Unrealized		No. of		Fair		Unrealized		No. of		Fair		Unrealized		No. of
	Value		Losses		Issuances		Value		Losses		Issuances		Value		Losses		Issuances
	(Dollars in thousands)
Securities Available-for-Sale
U.S. treasury securities	$	374,153	$	265		6	$	-	$	-		-	$	374,153	$	265		6
Mortgage-backed securities		-		-		-		425,090		6,386		16		425,090		6,386		16
Collateralized mortgage obligations		-		-		-		45		34		1		45		34		1
Corporate debt securities		-		-		-		63,753		1,247		4		63,753		1,247		4
Mutual funds		-		-		-		5,866		134		1		5,866		134		1
Preferred stock of government sponsored entities		2,448		3,733		2		-		-		-		2,448		3,733		2
Total securities available-for-sale	$	376,601	$	3,998		8	$	494,754	$	7,801		22	$	871,355	$	11,799		30

	As of December 31, 2013
	Temporarily Impaired Securities
	Less than 12 months						12 months or longer						Total
	Fair		Unrealized		No. of		Fair		Unrealized		No. of		Fair		Unrealized		No. of
	Value		Losses		Issuances		Value		Losses		Issuances		Value		Losses		Issuances
	(Dollars in thousands)
Securities Available-for-Sale
U.S. treasury securities	$	75,064	$	1		1	$	-	$	-		-	$	75,064	$	1		1
Mortgage-backed securities		792,012		64,526		25		272		2		7		792,284		64,528		32
Mortgage-backed securities-Non-agency		94		1		1		-		-		-		94		1		1
Collateralized mortgage obligations		68		4		2		301		50		3		369		54		5
Corporate debt securities		9,970		30		1		100,081		4,919		8		110,051		4,949		9
Mutual funds		-		-		-		5,724		275		1		5,724		275		1
Total securities available-for-sale	$	877,208	$	64,562		30	$	106,378	$	5,246		19	$	983,586	$	69,808		49