The amortized cost and fair value of investment securities are shown in the following tables. Management performs a quarterly evaluation of investment securities for any other-than-temporary impairment. During 2020, 2019 and 2018, there were no investment securities deemed to be other-than-temporarily impaired.


(In thousands)	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
2020:
Debt Securities Available-for-Sale
Obligations of states and political subdivisions	$	279,245	$	25,973	$	—	$	305,218
U.S. Government sponsored entities’ asset-backed securities	726,589		26,248		728		752,109
Corporate debt securities	2,000		14		—		2,014
Total	$	1,007,834	$	52,235	$	728	$	1,059,341


(In thousands)	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
2019:
Debt Securities Available-for-Sale
Obligations of states and political subdivisions	$	302,928	$	17,563	$	—	$	320,491
U.S. Government sponsored entities’ asset-backed securities	884,571		10,862		6,223		889,210
Total	$	1,187,499	$	28,425	$	6,223	$	1,209,701

The following table provides detail on investment securities with unrealized losses aggregated by investment category and length of time the individual securities had been in a continuous loss position at December 31, 2020 and December 31, 2019:


	Less than 12 Months				12 Months or Longer				Total
(In thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
2020:
Debt Securities Available-for-Sale
U.S. Government sponsored entities' asset-backed securities	$	86,393	$	695	$	4,727	$	33	$	91,120	$	728
Total	$	86,393	$	695	$	4,727	$	33	$	91,120	$	728


	Less than 12 Months				12 Months or Longer				Total
(In thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
2019:
Debt Securities Available-for-Sale
U.S. Government sponsored entities' asset-backed securities	$	237,613	$	1,106	$	171,805	$	5,117	$	409,418	$	6,223
Total	$	237,613	$	1,106	$	171,805	$	5,117	$	409,418	$	6,223

Management does not believe any individual unrealized loss as of December 31, 2020 or 2019 represented an other-than-temporary impairment. The unrealized loss on agency issued debt securities are primarily the result of interest rate changes. These conditions will not prohibit Park from receiving its contractual principal and interest payments on these debt securities. The fair value of these debt securities is expected to recover as payments are received on these securities and they approach maturity. Should the impairment of any of these securities become other-than-temporary, the cost basis of the investment will be reduced and the resulting loss attributable to credit will be recognized in net income in the period the other-than-temporary impairment is identified.

The amortized cost and estimated fair value of investments in debt securities at December 31, 2020, are shown in the following table by contractual maturity, except for asset-backed securities, which are shown as a single total, due to the unpredictability of the timing in principal repayments.


(In thousands)	Amortized Cost		Fair Value		Tax Equivalent Yield (1)
Debt Securities Available-for-Sale
Corporate debt securities
Due five through ten years	$	2,000	$	2,014	4.00	%

Obligations of states and political subdivisions
Due five through ten years	$	66,449	$	72,860	3.80	%
Due greater than ten years	212,796		232,358		3.67	%
Total	$	279,245	$	305,218	3.70	%

U.S. Government sponsored entities’ asset-backed securities	$	726,589	$	752,109	2.14	%

(1) The tax equivalent yield for obligations of states and political subdivisions includes the effects of a taxable equivalent adjustment using a 21% federal corporate income tax rate.

At December 31, 2020, investment securities with an amortized cost of $329 million were pledged for government and trust department deposits, $349 million were pledged to secure repurchase agreements and $14 million were pledged as collateral for FHLB advance borrowings. At December 31, 2019, investment securities with an amortized cost of $370 million were pledged for government and trust department deposits, $197 million were pledged to secure repurchase agreements and $18 million were pledged as collateral for FHLB advance borrowings.

At December 31, 2020, there were no holdings of securities of any one issuer, other than the U.S. Government and its agencies, in an amount greater than 10% of shareholders’ equity.

During 2020, Park sold certain AFS debt securities with a book value of $112.5 million at a gross loss of $64,000, and sold certain AFS debt securities with a book value of $196.4 million at a gross gain of $3.4 million. During 2019, Park sold certain AFS debt securities with a book value of $62.4 million at a gross loss of $692,000, and sold certain AFS debt securities with a book value of $29.1 million at a gross gain of $271,000. During 2018, Park sold certain AFS debt securities with a book value of $245.0 million at a gross loss of $2.6 million, sold certain AFS debt securities with a book value of $2.0 million at a gross gain of $60,000, and sold certain HTM debt securities with a book value of $7.4 million at a gross gain of $0.3 million. These HTM debt securities had been paid down by 96.3% of the principal outstanding at acquisition.

On September 1, 2019, Park adopted the portion of ASU 2019-04 which allowed for a one-time reclassification of securities from HTM to AFS. On that date, Park transferred HTM securities with a fair value of $373.9 million to the AFS classification. The transfer occurred at fair value and had a related unrealized gain, net of taxes, of $19.1 million recorded in other comprehensive income.

Other investment securities (as shown on the Consolidated Balance Sheets) consist of stock investments in the FHLB, the FRB, and equity securities. The FHLB and FRB restricted stock investments are carried at their redemption value. Equity securities with a readily determinable fair value are carried at fair value. Equity securities without a readily determinable fair value are recorded at cost, minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions ("modified cost"). Park's portfolio of equity investments in limited partnerships which provide mezzanine funding ("Partnership Investments") are valued using the net asset value practical expedient in accordance with ASC 820.


(In thousands)	December 31, 2020		December 31, 2019
FHLB stock	$	22,090	$	30,060
FRB stock	14,653		14,653
Equity investments carried at fair value	2,511		1,993
Equity investments carried at modified cost (1)	4,689		2,689
Equity investments carried at net asset value	21,522		20,411
Total other investment securities	$	65,465	$	69,806

During the year ended December 31, 2020, the FHLB repurchased 79,697 shares of FHLB stock with a book value of $8.0 million. No shares of FRB stock were purchased or sold in 2020. During the year ended December 31, 2019, the FHLB repurchased 133,281 shares of FHLB stock with a book value of $13.3 million. Additionally, during 2019, Park acquired Carolina Alliance's FHLB shares which were subsequently repurchased by the FHLB. Park purchased 128,553 shares of FRB stock with a book value of $6.4 million in 2019.

For the years ended December 31, 2020, 2019 and 2018, $(239,000), $345,000 and $(287,000), respectively, of unrealized (losses) gains on equity investments carried at fair value were recorded within "Gain on equity securities, net" on the Consolidated Statements of Income. An additional $3.5 million gain recorded within "Gain on equity securities, net" on the Consolidated Statement of Income for the year ended December 31, 2018 relates to Park's 8.55% investment in NewDominion Bank which merged with Park National Bank on July 1, 2018.

For the years ended December 31, 2020, 2019 and 2018, $2.4 million, $4.8 million and $1.4 million, respectively, of gains on equity investments carried at NAV were recorded within "Gain on equity securities, net" on the Consolidated Statements of Income.