The amortized cost and fair values of securities available for sale and held to maturity were as follows.

						Gross		Gross
				Amortized		Unrealized		Unrealized
December 31, 2014:				Cost		Gains		Losses			Fair Value
				($ in Thousands)
Investment securities available for sale:
	U.S. Treasury securities			$	999	$	0	$	(1)	$	998
	Obligations of state and political subdivisions
		(municipal securities)			560,839		21,869		(29)		582,679
	Residential mortgage-related securities:
			Government-sponsored enterprise ("GSE")		3,700,103		61,236		(30,550)		3,730,789
			Private-label		2,297		7		(10)		2,294
	GSE commercial mortgage-related securities				1,097,913		1,922		(25,942)		1,073,893
	Other securities (debt and equity)				6,108		51		0		6,159
			Total investment securities available for sale	$	5,368,259	$	85,085	$	(56,532)	$	5,396,812

Investment securities held to maturity:
	Obligations of state and political subdivisions
		(municipal securities)		$	404,455	$	9,444	$	(832)	$	413,067
			Total investment securities held to maturity	$	404,455	$	9,444	$	(832)	$	413,067


						Gross		Gross
				Amortized		Unrealized		Unrealized
December 31, 2013:				Cost		Gains		Losses			Fair Value
				($ in Thousands)
Investment securities available for sale:
	U. S. Treasury securities			$	1,001	$	1	$	-	$	1,002
	Obligations of state and political subdivisions
		(municipal securities)			653,758		23,855		(1,533)		676,080
	Residential mortgage-related securities:
			GSE		3,855,467		61,542		(78,579)		3,838,430
			Private-label		3,035		16		(37)		3,014
	GSE commercial mortgage-related securities				673,555		1,764		(27,842)		647,477
	Asset-backed securities⁽¹⁾				23,049		10		0		23,059
	Other securities (debt and equity)				60,711		855		(43)		61,523
			Total investment securities available for sale	$	5,270,576	$	88,043	$	(108,034)	$	5,250,585

Investment securities held to maturity:
	Obligations of state and political subdivisions
		(municipal securities)		$	175,210	$	401	$	(5,722)	$	169,889
			Total investment securities held to maturity	$	175,210	$	401	$	(5,722)	$	169,889


(1) The asset-backed securities position is largely comprised of senior, floating rate, tranches of student loan securities issued by SLM Corp and guaranteed under the Federal Family Education Loan Program.

The amortized cost and fair values of investment securities available for sale and held to maturity at December 31, 2014, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.



		Available for Sale					Held to Maturity
($ in Thousands)		Amortized Cost			Fair Value		Amortized Cost			Fair Value
Due in one year or less		$	33,912	$	34,122		$	0	$	0
Due after one year through five years			232,210		243,009			2,264		2,285
Due after five years through ten years			295,663		306,319			120,085		121,721
Due after ten years			6,143		6,336			282,106		289,061
	Total debt securities		567,928		589,786			404,455		413,067
Residential mortgage-related securities:
	GSE		3,700,103		3,730,789			-		-
	Private-label		2,297		2,294			-		-
GSE commercial mortgage-related securities			1,097,913		1,073,893			-		-
Equity securities			18		50			-		-
	Total investment securities	$	5,368,259	$	5,396,812		$	404,455	$	413,067
Ratio of Fair Value to Amortized Cost					100.5	%				102.1	%

For 2014, net investment securities gains were primarily attributable to gains on sales of debt securities. Net investment securities gains for 2013 were primarily attributable to gains on sales of municipal and debt securities, while for 2012, net investment securities gains were primarily attributable to gains on sales of equity, mortgage-related, and trust preferred debt securities.

Total proceeds and gross realized gains and losses from sales and write-downs of investment securities (with other-than-temporary write-downs on securities included in gross losses) for each of the three years ended December 31 were as follows.

		2014		2013		2012
		($ in Thousands)
Gross gains		$	1,184	$	637	$	4,481
Gross losses			(690)		(73)		(220)
	Investment securities gains, net	$	494	$	564	$	4,261
Proceeds from sales of investment securities			102,011		136,152		299,782

Pledged securities with a carrying value of approximately $2.8 billion and $2.9 billion at December 31, 2014, and December 31, 2013, respectively, were pledged to secure certain deposits or for other purposes as required or permitted by law.

The following represents gross unrealized losses and the related fair value of investment securities available for sale and held to maturity, aggregated by investment category and length of time individual securities have been in a continuous unrealized loss position, at December 31, 2014.

			Less than 12 months					12 months or more					Total
			Number					Number
			of	Unrealized			Fair	of	Unrealized			Fair	Unrealized			Fair
December 31, 2014			Securities		Losses		Value	Securities		Losses		Value		Losses		Value
			($ in Thousands)
Investment securities available for sale:
	U.S. Treasury securities		1		(1)		998			-		-		(1)		998
	Obligations of state and political
		subdivisions (municipal securities)	6	$	(9)	$	3,374	6	$	(20)	$	2,133	$	(29)	$	5,507
	Residential mortgage-related securities:
		GSE	16		(1,404)		333,713	56		(29,146)		1,256,533		(30,550)		1,590,246
		Private-label	1		(9)		1,772	2		(1)		27		(10)		1,799
	GSE commercial mortgage-related securities		9		(1,766)		329,982	20		(24,176)		460,425		(25,942)		790,407
		Total		$	(3,189)	$	669,839		$	(53,343)	$	1,719,118	$	(56,532)	$	2,388,957

Investment securities held to maturity:
	Obligations of state and political
		subdivisions (municipal securities)	74	$	(216)	$	31,924	85	$	(616)	$	38,915	$	(832)	$	70,839
		Total		$	(216)	$	31,924		$	(616)	$	38,915	$	(832)	$	70,839

The Corporation reviews the investment securities portfolio on a quarterly basis to monitor its exposure to other-than-temporary impairment. A determination as to whether a security's decline in fair value is other-than-temporary takes into consideration numerous factors and the relative significance of any single factor can vary by security. Some factors the Corporation may consider in the other-than-temporary impairment analysis include, the length of time and extent to which the security has been in an unrealized loss position, changes in security ratings, financial condition and near-term prospects of the issuer, as well as security and industry specific economic conditions. In addition, with regards to its debt securities, the Corporation may also evaluate payment structure, whether there are defaulted payments or expected defaults, prepayment speeds, and the value of any underlying collateral.

Based on the Corporation's evaluation, management does not believe any unrealized loss at December 31, 2014, represents an other-than-temporary impairment as these unrealized losses are primarily attributable to changes in interest rates and the current market conditions, and not credit deterioration. The unrealized losses reported for residential mortgage-related securities relate to private-label residential mortgage-related securities as well as residential mortgage-related securities issued by government sponsored enterprises such as the Government National Mortgage Association ("GNMA"), the Federal National Mortgage Association (“FNMA”) and the Federal Home Loan Mortgage Corporation (“FHLMC”). The unrealized losses reported for commercial mortgage related securities relate to securities issued by GNMA. The unrealized losses reported for municipal securities relate to various state and local political subdivisions and school districts. The Corporation currently does not intend to sell nor does it believe that it will be required to sell the securities contained in the above unrealized losses table before recovery of their amortized cost basis. The improvement in the unrealized loss position of the investment securities portfolio was due to a reduction in the overall level of interest rates for 2014, as well as spread compression on mortgage-related and municipal securities, which increased the fair value of investment securities.

The following is a summary of the credit loss portion of other-than-temporary impairment recognized in earnings on debt securities during 2013 and 2014.

	Private-label
	Mortgage-Related		Trust Preferred
	Securities		Debt Securities			Total
	$ in Thousands
Balance of credit-related other-than-temporary impairment at December 31, 2012	$	(532)	$	(6,336)	$	(6,868)
Reduction due to credit impaired securities sold		532		57		589
Balance of credit-related other-than-temporary impairment at December 31, 2013	$	0	$	(6,279)	$	(6,279)
Reduction due to credit impaired securities sold or abandoned		0		6,279		6,279
Balance of credit-related other-than-temporary impairment at December 31, 2014	$	0	$	0	$	0

For comparative purposes, the following represents gross unrealized losses and the related fair value of investment securities available for sale and held to maturity, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at December 31, 2013.

			Less than 12 months					12 months or more				Total
		Number					Number
		of		Unrealized		Fair	of		Unrealized		Fair		Unrealized		Fair
December 31, 2013		Securities		Losses		Value	Securities	Losses			Value	Losses			Value
			($ in Thousands)
Investment securities available for sale:
Obligations of state and political
	subdivisions (municipal securities)	113	$	(1,525)	$	47,044	1	$	(8)	$	273	$	(1,533)	$	47,317
Residential mortgage-related securities:
	GSE	106		(57,393)		1,887,784	15		(21,186)		421,082		(78,579)		2,308,866
	Private-label	2		(37)		2,105	1		-		35		(37)		2,140
GSE commercial mortgage-related securities		19		(23,854)		443,462	1		(3,988)		45,950		(27,842)		489,412
Other securities (debt)		5		(43)		6,452	-		-		-		(43)		6,452
	Total		$	(82,852)	$	2,386,847		$	(25,182)	$	467,340	$	(108,034)	$	2,854,187

Investment securities held to maturity:
Obligations of state and political
	subdivisions (municipal securities)	298	$	(5,339)	$	124,435	10	$	(383)	$	5,010	$	(5,722)	$	129,445
	Total		$	(5,339)	$	124,435		$	(383)	$	5,010	$	(5,722)	$	129,445

Federal Home Loan Bank (“FHLB”) and Federal Reserve Bank Stocks: The Corporation is required to maintain Federal Reserve stock and FHLB stock as a member of both the Federal Reserve System and the FHLB, and in amounts as required by these institutions. These equity securities are “restricted” in that they can only be sold back to the respective institutions or another member institution at par. Therefore, they are less liquid than other marketable equity securities and their fair value is equal to amortized cost. At December 31, 2014, and 2013, the Corporation had FHLB stock of $118 million and $110 million, respectively. The Corporation had Federal Reserve Bank stock of $71 million and $71 million at December 31, 2014 and 2013, respectively.