Investment securities are classified as available for sale, held to maturity, or equity on the consolidated balance sheets at the time of purchase. See Note 1 for the Corporation’s accounting policy for investment securities. The amortized cost and fair values of securities available for sale and held to maturity at December 31, 2019 were as follows:


($ 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)^(a)	$	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)^(a)	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

(a) As permitted by ASU 2019-04, which was adopted during the third quarter of 2019, the Corporation made a one-time election during the third quarter of 2019 to transfer municipal securities with an amortized cost of $692 million from held to maturity to available for sale.


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


Investment securities available for sale
U.S. Treasury securities	$	1,000	$	—	$	(1)	$	999
Residential mortgage-related securities:
FNMA / FHLMC	296,296		2,466		(3,510)		295,252
GNMA	2,169,943		473		(41,885)		2,128,531
Private-label	1,007		—		(4)		1,003
GNMA commercial mortgage-related securities	1,273,309		—		(52,512)		1,220,797
FFELP asset-backed securities	297,347		711		(698)		297,360
Other debt securities	3,000		—		—		3,000
Total investment securities available for sale	$	4,041,902	$	3,649	$	(98,610)	$	3,946,941
Investment securities held to maturity
Obligations of state and political subdivisions (municipal securities)	$	1,790,683	$	8,255	$	(15,279)	$	1,783,659
Residential mortgage-related securities
FNMA / FHLMC	92,788		169		(1,795)		91,162
GNMA	351,606		1,611		(8,181)		345,035
GNMA commercial mortgage-related securities	505,434		7,559		(22,579)		490,414
Total investment securities held to maturity	$	2,740,511	$	17,593	$	(47,835)	$	2,710,271

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 December 31, 2019, 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	$	2,795	$	2,800		$	29,033	$	29,218
Due after one year through five years	32,399		32,901			82,023		83,245
Due after five years through ten years	317,292		326,361			136,138		140,704
Due after ten years	180,422		187,098			1,172,373		1,235,077
Total debt securities	532,908		549,160			1,419,568		1,488,245
Residential mortgage-related securities
FNMA / FHLMC	131,158		132,660			81,676		83,420
GNMA	982,941		985,139			269,523		270,296

Commercial mortgage-related securities
FNMA / FHLMC	19,929		21,728			—		—
GNMA	1,314,836		1,310,207			434,317		434,503
FFELP asset-backed securities	270,178		263,693			—		—
Total investment securities	$	3,251,950	$	3,262,586		$	2,205,083	$	2,276,465
Ratio of Fair Value to Amortized Cost			100.3		%			103.2		%

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 and write-up of investment securities for each of the three years ended December 31 are shown below. There were no other-than-temporary impairment write-downs on investment securities for 2019, 2018, or 2017.


($ in Thousands)	2019		2018		2017
Gross gains on available for sale securities	$	6,374	$	1,954	$	—
Gross gains on held to maturity securities	—		—		439
Total gains	6,374		1,954		439
Gross (losses) on available for sale securities	(13,861)		(3,938)		—
Gross (losses) on held to maturity securities	—		—		(5)
Total (losses)	(13,861)		(3,938)		(5)
Write-up of equity securities without readily determinable fair values	13,444		—		—
Investment securities gains (losses), net	$	5,957	$	(1,985)	$	434
Proceeds from sales of investment securities	$	1,367,476	$	601,130	$	18,467

During the third quarter 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 during the quarter. The Corporation sold shorter duration, lower yielding municipal securities that were included in the transfer for proceeds of $157 million at a gain of $3 million, with the proceeds being reinvested into longer duration, higher yielding held to maturity municipal securities. Additionally, during the first nine months of 2019, the Corporation sold $1.2 billion of taxable, floating rate ABS and shorter duration MBS, CMBS, and CMOs 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 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.

During 2018, the Corporation executed a strategy to improve the yield on securities and increase interest income during the current and future calendar years. During the third quarter of 2018, the Corporation sold mortgage-related securities totaling approximately $108 million at a slight gain with all proceeds reinvested into higher yielding securities. The tax equivalent yield of the securities sold was 3.08% while the reinvestment was at 3.51%. During the second quarter of 2018, the Corporation also sold $40 million of lower yielding GNMA commercial mortgage-related securities.

In addition, on February 1, 2018, the date the Bank Mutual acquisition was completed, the Corporation sold Bank Mutual's entire $453 million securities portfolio. The Corporation originally reinvested the proceeds from the Bank Mutual securities portfolio into GNMA residential mortgage-related securities with the goal of reinvesting future cash flows into municipal securities. That strategy was completed during August 2018.

During 2017, the Corporation sold approximately $18 million of municipal securities classified as held to maturity due to significant credit concerns and negative actions taken by credit rating agencies, primarily as a result of budgetary pressures in the State of Illinois and State of Connecticut. These sales resulted in a net gain of approximately $434,000.

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, 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

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, 2018:


	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
U.S. Treasury securities	—	$	—	$	—	1	$	(1)	$	999	$	(1)	$	999

Residential mortgage-related securities
FNMA / FHLMC	15	(31)		17,993		17	(3,479)		189,405		(3,510)		207,398
GNMA	12	(4,529)		452,183		79	(37,355)		1,598,159		(41,885)		2,050,342
Private-label	1	(4)		1,003		—	—		—		(4)		1,003
GNMA commercial mortgage-related securities	—	—		—		93	(52,512)		1,220,854		(52,512)		1,220,854
FFELP asset-backed securities	13	(698)		142,432		—	—		—		(698)		142,432

Total	41	$	(5,262)	$	613,612	190	$	(93,347)	$	3,009,417	$	(98,610)	$	3,623,028
Investment securities held to maturity
Obligations of state and political subdivisions (municipal securities)	272	$	(2,860)	$	313,212	752	$	(12,419)	$	509,374	$	(15,279)	$	822,586
Residential mortgage-related securities
FNMA / FHLMC	13	(780)		57,896		22	(1,015)		28,888		(1,795)		86,784
GNMA	13	(414)		19,822		66	(7,767)		320,387		(8,181)		340,209
GNMA commercial mortgage-related securities	—	—		—		25	(22,579)		490,414		(22,579)		490,414
Total	298	$	(4,053)	$	390,929	865	$	(43,780)	$	1,349,063	$	(47,835)	$	1,739,992

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

Based on the Corporation’s evaluation, management does not believe any unrealized loss at December 31, 2019 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 municipal securities relate to various state and local political subdivisions and school districts. The unrealized losses at December 31, 2019 for mortgage-related securities have declined due to the decrease in overall interest rates. The U.S. Treasury 3 year and 5 year rates decreased by 84 bp and 82 bp, respectively, from December 31, 2018. 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 stock and FHLB stock as a member bank 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, 2019 and 2018, the Corporation had FHLB stock of $149 million and $173 million, respectively. The Corporation had Federal Reserve Bank stock of $78 million and $77 million at December 31, 2019 and 2018, respectively.

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 December 31, 2019 and 2018, the Corporation had equity securities with readily determinable fair values of $2 million.

Equity securities without readily determinable fair values: The Corporation's portfolio of equity securities without readily determinable fair values consists of Visa Class B restricted shares that the Corporation received in 2008 as part of Visa's initial public offering. During the second quarter of 2019, the Corporation donated 42,039 shares of Visa Class B restricted shares to the Corporation's Charitable Remainder Trust, and the subsequent sale of those shares by the Trust resulted in an observable market price. As a result, the Corporation wrote up their remaining 77,000 Visa Class B restricted shares to fair value. Based on the existing transfer restriction and the uncertainty of the covered litigation, the Visa Class B restricted shares were previously carried at a zero cost basis. Thus, the Corporation had equity securities without readily determinable fair values of $13 million at December 31, 2019 and $0 at December 31, 2018.