Investment securities are classified as available for sale, held to maturity, or equity on the consolidated balance sheets at the time of purchase. The amortized cost and fair values of securities available for sale and held to maturity at June 30, 2020 were as follows:


($ in Thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Fair Value


Investment securities available for sale
U. S. Treasury securities	$	26,646	$	88	$	—	$	26,735
Agency securities	24,982		25		—		25,007
Obligations of state and political subdivisions (municipal securities)	471,346		24,542		—		495,888
Residential mortgage-related securities
FNMA / FHLMC	813,458		4,652		—		818,110
GNMA	592,338		13,222		—		605,561

Commercial mortgage-related securities
FNMA / FHLMC	19,793		2,269		—		22,061
GNMA	782,577		20,786		—		803,362
Asset backed securities
FFELP	356,532		—		(16,058)		340,474
SBA	9,619		—		(44)		9,575

Other debt securities	3,000		—		—		3,000
Total investment securities available for sale	$	3,100,291	$	65,584	$	(16,102)	$	3,149,773
Investment securities held to maturity
U. S. Treasury securities	$	999	$	36	$	—	$	1,036
Obligations of state and political subdivisions (municipal securities)	1,435,938		110,132		(53)		1,546,018
Residential mortgage-related securities
FNMA / FHLMC	71,872		3,400		—		75,271
GNMA	207,908		7,012		—		214,920
GNMA commercial mortgage-related securities	360,570		11,691		—		372,261
Total investment securities held to maturity	$	2,077,287	$	132,271	$	(53)	$	2,209,505


($ in Thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized (Losses)		Fair Value


Investment securities available for sale

Obligations of state and political subdivisions (municipal securities)	$	529,908	$	16,269	$	(18)	$	546,160
Residential mortgage-related securities
FNMA / FHLMC	131,158		1,562		(59)		132,660
GNMA	982,941		3,887		(1,689)		985,139

Commercial mortgage-related securities
FNMA / FHLMC	19,929		1,799		—		21,728
GNMA	1,314,836		7,403		(12,032)		1,310,207
FFELP asset backed securities	270,178		—		(6,485)		263,693

Other debt securities	3,000		—		—		3,000
Total investment securities available for sale	$	3,251,950	$	30,920	$	(20,284)	$	3,262,586
Investment securities held to maturity
U. S. Treasury securities	$	999	$	19	$	—	$	1,018
Obligations of state and political subdivisions (municipal securities)	1,418,569		69,775		(1,118)		1,487,227
Residential mortgage-related securities
FNMA / FHLMC	81,676		1,759		(15)		83,420
GNMA	269,523		1,882		(1,108)		270,296
GNMA commercial mortgage-related securities	434,317		6,308		(6,122)		434,503
Total investment securities held to maturity	$	2,205,083	$	79,744	$	(8,363)	$	2,276,465

Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. The expected maturities of investment securities available for sale and held to maturity at June 30, 2020 are shown below:


	Available for Sale							Held to Maturity
($ in Thousands)	Amortized Cost		Fair Value			Amortized Cost		Fair Value
Due in one year or less	$	9,427	$	9,458		$	33,745	$	33,927
Due after one year through five years	83,136		83,882			67,917		69,887
Due after five years through ten years	343,084		360,051			166,553		175,189
Due after ten years	90,327		97,240			1,168,722		1,268,050
Total debt securities	525,975		550,630			1,436,937		1,547,053
Residential mortgage-related securities
FNMA / FHLMC	813,458		818,110			71,872		75,271
GNMA	592,338		605,561			207,908		214,920

Commercial mortgage-related securities
FNMA / FHLMC	19,793		22,061			—		—
GNMA	782,577		803,362			360,570		372,261
Asset backed securities
FFELP	356,532		340,474			—		—
SBA	9,619		9,575			—		—

Total investment securities	$	3,100,291	$	3,149,773		$	2,077,287	$	2,209,505
Ratio of fair value to amortized cost			101.6		%			106.4		%


($ in Thousands)	AAA		AA		A		Total
U. S. Treasury securities	$	999	$	—	$	—	$	999
Obligations of state and political subdivisions (municipal securities)	561,670		853,910		20,358		1,435,938
Residential mortgage-related securities
FNMA/FHLMC	71,872		—		—		71,872
GNMA	207,908		—		—		207,908
GNMA commercial mortgage-related securities	360,570		—		—		360,570
Total held to maturity securities	$	1,203,018	$	853,910	$	20,358	$	2,077,287

Investment securities gains (losses), net includes proceeds from the sale of investment securities as well as any applicable write-ups or write-downs of investment securities. The proceeds from the sale of investment securities for the three and six months ended June 30, 2020 and 2019 are shown below:


	Three Months Ended June 30,						Six Months Ended June 30,
($ in Thousands)	2020		2019		2020		2019
Gross gains on available for sale securities	$	3,106	$	654	$	9,304	$	2,334
Gross gains on held to maturity securities	—		—		—		—
Total gains	3,106		654		9,304		2,334
Gross (losses) on available for sale securities	(11)		(13,636)		(90)		(13,636)
Gross (losses) on held to maturity securities	—		—		—		—
Total (losses)	(11)		(13,636)		(90)		(13,636)
Write-up of equity securities without readily determinable fair values	—		13,444		—		13,444
Investment securities gains (losses), net	$	3,096	$	463	$	9,214	$	2,143
Proceeds from sales of investment securities	$	261,037	$	803,105	$	626,276	$	934,228

During the second quarter of 2020, the Corporation sold $261 million of less liquid securities at a gain of $3 million, reinvesting the proceeds into more liquid securities in order to further improve portfolio liquidity. During the first quarter of 2020, the Corporation sold $281 million of primarily prepayment sensitive mortgage-related securities at a gain of $6 million. Additionally, in February 2020, the Corporation sold $84 million of certain securities acquired in the First Staunton acquisition that did not fit the parameters of the Corporation's current investment strategy.

During the first six months of 2019, the Corporation sold $934 million of taxable floating rate ABS and shorter duration MBS, and CMO Agency securities, with the proceeds utilized to pay down borrowings and to reinvest into higher yielding Agency related mortgage securities with slightly longer durations, repositioning the portfolio for a stable to declining rate environment. The Corporation also donated 42,039 shares of Visa Class B restricted shares to the Corporation's Charitable Remainder Trust during the second quarter of 2019, and the subsequent sale of those shares by the Trust resulted in an observable market price. As a result, the Corporation wrote up its remaining 77,000 Visa Class B restricted shares to fair value. Based on the existing transfer restriction and the uncertainty of covered litigation, the shares were previously carried at a zero cost basis.

Accrued interest receivable on held to maturity securities totaled $15 million and $16 million at June 30, 2020 and December 31, 2019, respectively. Accrued interest receivable on available for sale securities totaled $9 million and $10 million at June 30, 2020 and December 31, 2019, respectively. Accrued interest receivable on both held to maturity and available for sale securities is included in interest receivable on the consolidated balance sheets. There was no interest income reversed for investments going into nonaccrual at June 30, 2020 or December 31, 2019.

The allowance for credit losses on held to maturity securities was approximately $61,000 at June 30, 2020, attributable entirely to the Corporation's municipal securities, included in investment securities held to maturity, net, at amortized cost on the consolidated balance sheets. The Corporation also holds U.S. Treasury and residential mortgage-related securities issued by the U.S. government or a GSE which are backed by the full faith and credit of the U.S. government and, as a result, no allowance for credit losses has been recorded related to these securities.

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 June 30, 2020:


	Less than 12 months								12 months or more						Total
($ in Thousands)	Number of Securities	Unrealized (Losses)		Fair Value		Number of Securities	Unrealized (Losses)		Fair Value		Unrealized (Losses)		Fair Value
Investment securities available for sale


Obligations of state and political subdivisions (municipal securities)	1	$	—	$	548	—	$	—	$	—	$	—	$	548

FNMA / FHLMC residential mortgage-related securities	5	—		54,893		—	—		—		—		54,893



Asset backed securities
FFELP	9	(5,478)		147,310		17	(10,580)		193,164		(16,058)		340,474
SBA	15	(44)		9,422		—	—		—		(44)		9,422


Total	30	$	(5,522)	$	212,172	17	$	(10,580)	$	193,164	$	(16,102)	$	405,336
Investment securities held to maturity
Obligations of state and political subdivisions (municipal securities)	8	$	(52)	$	12,431	2	$	(1)	$	365	$	(53)	$	12,796




Total	8	$	(52)	$	12,431	2	$	(1)	$	365	$	(53)	$	12,796

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, 2019:


	Less than 12 months								12 months or more						Total
($ in Thousands)	Number of Securities	Unrealized (Losses)		Fair Value		Number of Securities	Unrealized (Losses)		Fair Value		Unrealized (Losses)		Fair Value
Investment securities available for sale

Obligations of state and political subdivisions (municipal securities)	4	$	(18)	$	1,225	—	$	—	$	—	$	(18)	$	1,225
Residential mortgage-related securities
FNMA / FHLMC	—	—		—		4	(59)		34,807		(59)		34,807
GNMA	18	(924)		322,394		3	(766)		79,461		(1,689)		401,856

GNMA commercial mortgage-related securities	22	(810)		258,218		42	(11,222)		621,307		(12,032)		879,524
FFELP asset backed securities	19	(6,092)		250,780		2	(393)		12,913		(6,485)		263,693
Other debt securities	2	—		2,000		—	—		—		—		2,000

Total	65	$	(7,843)	$	834,616	51	$	(12,440)	$	748,487	$	(20,284)	$	1,583,104
Investment securities held to maturity
Obligations of state and political subdivisions (municipal securities)	52	$	(1,105)	$	77,562	6	$	(13)	$	2,378	$	(1,118)	$	79,940
Residential mortgage-related securities
FNMA / FHLMC	1	(6)		1,242		1	(9)		833		(15)		2,075
GNMA	12	(1,059)		187,261		8	(49)		6,587		(1,108)		193,849
GNMA commercial mortgage-related securities	2	(29)		26,202		21	(6,093)		357,733		(6,122)		383,935
Total	67	$	(2,199)	$	292,267	36	$	(6,164)	$	367,532	$	(8,363)	$	659,799

The Corporation reviews the available for sale investment securities portfolio on a quarterly basis to monitor its credit exposure. A determination as to whether a security’s decline in fair value is the result of credit risk 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 impairment analysis include the extent to which the security has been in an unrealized loss position, the change in security rating, financial condition and near-term prospects of the issuer, as well as the security and industry specific economic conditions.

Based on the Corporation’s evaluation, management does not believe any available for sale securities in an unrealized loss position at June 30, 2020 represent credit deterioration as these unrealized losses are primarily attributable to changes in interest rates and the current market conditions. The fair value of municipal securities, which pertains to various state and local political subdivisions and school districts, has increased due to the decrease in overall interest rates, resulting in lower unrealized losses at June 30, 2020. The U.S. Treasury 3 year and 5 year rates decreased by 144 bp and 140 bp, respectively, from December 31,

FHLB and Federal Reserve Bank stocks: The Corporation is required to maintain Federal Reserve Bank 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 June 30, 2020 and December 31, 2019, the Corporation had FHLB stock of $126 million and $149 million, respectively. The Corporation had Federal Reserve Bank stock of $81 million and $78 million at June 30, 2020 and December 31, 2019, respectively. Accrued interest receivable on FHLB stock totaled $2 million at both June 30, 2020 and December 31, 2019. There was no accrued interest receivable on Federal Reserve Bank stock at either June 30, 2020 or December 31, 2019. Accrued interest receivable on both FHLB stock and Federal Reserve Bank stock is included in interest receivable on the consolidated balance sheets.

Equity securities with readily determinable fair values: The Corporation's portfolio of equity securities with readily determinable fair values is primarily comprised of CRA Qualified Investment mutual funds. At both June 30, 2020 and December 31, 2019, the Corporation had equity securities with readily determinable fair values of $2 million.