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 September 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	$	26,541	$	108	$	—	$	26,650
Agency securities	24,983		50		—		25,033
Obligations of state and political subdivisions (municipal securities)	450,174		24,521		—		474,695
Residential mortgage-related securities
FNMA / FHLMC	1,267,003		9,554		(94)		1,276,463
GNMA	399,490		7,823		—		407,313

Commercial mortgage-related securities
FNMA / FHLMC	19,724		2,153		—		21,877
GNMA	670,573		17,805		—		688,378
Asset backed securities
FFELP	332,398		—		(6,556)		325,843
SBA	9,159		—		(48)		9,111

Other debt securities	3,000		—		(3)		2,997
Total investment securities available for sale	$	3,203,046	$	62,015	$	(6,701)	$	3,258,360
Investment securities held to maturity
U. S. Treasury securities	$	999	$	31	$	—	$	1,030
Obligations of state and political subdivisions (municipal securities)	1,444,325		115,343		(368)		1,559,300
Residential mortgage-related securities
FNMA / FHLMC	63,142		3,147		—		66,289
GNMA	159,455		5,217		—		164,672
Commercial mortgage-related securities
FNMA/FHLMC	11,220		—		—		11,220
GNMA	311,798		10,142		—		321,941
Total investment securities held to maturity	$	1,990,940	$	133,880	$	(368)	$	2,124,452


($ 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 September 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	$	8,343	$	8,350		$	28,957	$	29,140
Due after one year through five years	82,198		82,964			63,630		65,751
Due after five years through ten years	344,172		362,247			161,769		170,223
Due after ten years	69,987		75,815			1,190,968		1,295,217
Total debt securities	504,699		529,375			1,445,325		1,560,331
Residential mortgage-related securities
FNMA / FHLMC	1,267,003		1,276,463			63,142		66,289
GNMA	399,490		407,313			159,455		164,672

Commercial mortgage-related securities
FNMA / FHLMC	19,724		21,877			11,220		11,220
GNMA	670,573		688,378			311,798		321,941
Asset backed securities
FFELP	332,398		325,843			—		—
SBA	9,159		9,111			—		—

Total investment securities	$	3,203,046	$	3,258,360		$	1,990,940	$	2,124,452
Ratio of fair value to amortized cost			101.7		%			106.7		%


($ in Thousands)	AAA		AA		A		Total
U. S. Treasury securities	$	999	$	—	$	—	$	999
Obligations of state and political subdivisions (municipal securities)	567,468		860,465		16,393		1,444,325
Residential mortgage-related securities
FNMA/FHLMC	63,142		—		—		63,142
GNMA	159,455		—		—		159,455
Commercial mortgage-related securities
FNMA/FHLMC	11,220		—		—		11,220
GNMA	311,798		—		—		311,798
Total held to maturity securities	$	1,114,082	$	860,465	$	16,393	$	1,990,940

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 nine months ended September 30, 2020 and 2019 are shown below:


	Three Months Ended September 30,				Nine Months Ended September 30,
($ in Thousands)	2020		2019		2020		2019
Gross gains on available for sale securities	$	7	$	4,013	$	9,312	$	6,347
Gross gains on held to maturity securities	—		—		—		—
Total gains	7		4,013		9,312		6,347
Gross (losses) on available for sale securities	—		(225)		(90)		(13,861)
Gross (losses) on held to maturity securities	—		—		—		—
Total (losses)	—		(225)		(90)		(13,861)
Write-up of equity securities without readily determinable fair values	—		—		—		13,444
Investment securities gains (losses), net	$	7	$	3,788	$	9,222	$	5,931
Proceeds from sales of investment securities	$	8	$	433,222	$	626,283	$	1,367,450

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 nine months of 2019, the Corporation made a one-time election to transfer municipal securities with an amortized cost of $692 million from held to maturity to available for sale, as permitted by the adoption of ASU 2019-04. The Corporation sold $1.2 billion 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 $13 million and $16 million at September 30, 2020 and December 31, 2019, respectively. Accrued interest receivable on available for sale securities totaled $9 million and $10 million at September 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 September 30, 2020 or December 31, 2019.

The allowance for credit losses on held to maturity securities was approximately $70,000 at September 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 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 September 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



Residential mortgage-related securities
FNMA / FHLMC	5	$	(94)	$	77,157	—	$	—	$	—	$	(94)	$	77,157
GNMA	1	—		424		—	—		—		—		424


Asset backed securities
FFELP	5	(837)		93,134		20	(5,719)		232,709		(6,556)		325,843
SBA	15	(48)		8,953		—	—		—		(48)		8,953
Other debt securities	3	(3)		2,997		—	—		—		(3)		2,997

Total	29	$	(982)	$	182,665	20	$	(5,719)	$	232,709	$	(6,701)	$	415,374
Investment securities held to maturity
Obligations of state and political subdivisions (municipal securities)	10	$	(368)	$	25,895	—	$	—	$	—	$	(368)	$	25,895




Total	10	$	(368)	$	25,895	—	$	—	$	—	$	(368)	$	25,895

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 September 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 September 30, 2020. The U.S. Treasury 3 year and 5 year rates decreased by 146 bp and 141 bp, respectively, from December 31, 2019. The Corporation does not intend to sell nor does it believe that it will be required to sell the securities in an unrealized loss position before recovery of their amortized cost basis.

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 September 30, 2020 and December 31, 2019, the Corporation had FHLB stock of $82 million and $149 million, respectively. The Corporation had Federal Reserve Bank stock of $87 million and $78 million at September 30, 2020 and December 31, 2019, respectively. Accrued interest receivable on FHLB stock totaled $1 million and $2 million at September 30, 2020 and December 31, 2019. There was approximately $149,000 of accrued interest receivable on Federal Reserve Bank stock at September 30, 2020 and none at 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 September 30, 2020 and December 31, 2019, the Corporation had equity securities with readily determinable fair values of $2 million.