The amortized cost, gross unrealized gains and losses and estimated fair value of securities at September 30, 2020 and December 31, 2019 are summarized as follows (in thousands):


	September 30, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Allowance for Credit Losses		Fair Value
Available-for-Sale:
U.S. Government and agency obligations	$	169,740	$	1,140	$	(967)	$	—	$	169,913
Municipal bonds	257,056		15,707		(355)		—		272,408
Corporate bonds	53,756		2,300		(85)		—		55,971
Mortgage-backed or related securities	1,199,816		51,199		(515)		—		1,250,500
Asset-backed securities	9,701		51		(160)		—		9,592

	$	1,690,069	$	70,397	$	(2,082)	$	—	$	1,758,384


	September 30, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value		Allowance for Credit Losses
Held-to-Maturity:
U.S. Government and agency obligations	$	341	$	10	$	—	$	351	$	—
Municipal bonds	377,019		19,260		(593)		395,686		(60)
Corporate bonds	3,254		—		(13)		3,241		(42)
Mortgage-backed or related securities	48,521		3,007		—		51,528		—
	$	429,135	$	22,277	$	(606)	$	450,806	$	(102)


	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Trading:


Corporate bonds	$	27,203					$	25,636


	$	27,203					$	25,636
Available-for-Sale:
U.S. Government and agency obligations	$	90,468	$	286	$	(1,156)	$	89,598
Municipal bonds	101,927		5,233		(3)		107,157
Corporate bonds	4,357		14		(6)		4,365
Mortgage-backed or related securities	1,324,999		20,325		(3,013)		1,342,311
Asset-backed securities	8,195		—		(69)		8,126

	$	1,529,946	$	25,858	$	(4,247)	$	1,551,557
Held-to-Maturity:
U.S. Government and agency obligations	$	385	$	4	$	—	$	389
Municipal bonds	177,208		3,733		(2,213)		178,728
Corporate bonds	3,353		—		(11)		3,342
Mortgage-backed or related securities	55,148		921		(723)		55,346
	$	236,094	$	4,658	$	(2,947)	$	237,805

Accrued interest receivable on held-to-maturity debt securities was $2.9 million and $1.1 million as of September 30, 2020 and December 31, 2019, respectively, and was $6.1 million and $4.8 million on available-for-sale debt securities as of September 30, 2020 and December 31, 2019, respectively. Accrued interest receivable on securities is reported in accrued interest receivable on the consolidated statements of financial condition and is excluded from the calculation of the allowance for credit losses.

At September 30, 2020, the gross unrealized losses and the fair value for securities available-for-sale aggregated by the length of time that individual securities have been in a continuous unrealized loss position were as follows (in thousands):


	September 30, 2020
	Less Than 12 Months				12 Months or More				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Available-for-Sale:
U.S. Government and agency obligations	$	3,162	$	(7)	$	53,105	$	(960)	$	56,267	$	(967)



Municipal bonds	16,636		(355)		—		—		16,636		(355)
Corporate bonds	11,205		(85)		—		—		11,205		(85)





Mortgage-backed or related securities	75,459		(500)		1,558		(15)		77,017		(515)



Asset-backed securities	870		(16)		6,469		(144)		7,339		(160)

	$	107,332	$	(963)	$	61,132	$	(1,119)	$	168,464	$	(2,082)

At December 31, 2019, the gross unrealized losses and the fair value for securities available-for-sale and held-to-maturity aggregated by the length of time that individual securities have been in a continuous unrealized loss position were as follows (in thousands):


	December 31, 2019
	Less Than 12 Months				12 Months or More				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Available-for-Sale:
U.S. Government and agency obligations	$	2,747	$	(20)	$	60,979	$	(1,136)	$	63,726	$	(1,156)



Municipal bonds	1,902		—		494		(3)		2,396		(3)
Corporate bonds	594		(6)		—		—		594		(6)




Mortgage-backed or related securities	300,852		(2,829)		33,360		(184)		334,212		(3,013)



Asset-backed securities	1,204		(17)		5,989		(52)		7,193		(69)

	$	307,299	$	(2,872)	$	100,822	$	(1,375)	$	408,121	$	(4,247)
Held-to-Maturity
U.S. Government and agency obligations	$	—	$	—	$	—	$	—	$	—	$	—
Municipal bonds	44,605		(1,889)		19,017		(324)		63,622		(2,213)
Corporate bonds	—		—		489		(11)		489		(11)
Mortgage-backed or related securities	11,117		(723)		—		—		11,117		(723)
	$	55,722	$	(2,612)	$	19,506	$	(335)	$	75,228	$	(2,947)

At September 30, 2020, there were 64 securities—available-for-sale with unrealized losses, compared to 90 at December 31, 2019. At December 31, 2019, there were 17 securities—held-to-maturity with unrealized losses. Management does not believe that any individual unrealized loss as of September 30, 2020 resulted from credit loss or that any individual unrealized loss represented other-than-temporary impairment (OTTI) as of December 31, 2019. The decline in fair market value of these securities was generally due to changes in interest rates and changes in market-desired spreads subsequent to their purchase.

There were no sales of securities—trading during the nine months ended September 30, 2020 or 2019. There were no securities—trading in a nonaccrual status at September 30, 2020 or December 31, 2019. Net unrealized holding losses of $2.4 million were recognized during the nine months ended September 30, 2020 compared to $172,000 of net unrealized holding losses recognized during the nine months ended September 30, 2019.

There were 30 sales of securities—available-for-sale during the nine months ended September 30, 2020, with a net gain of $296,000. There were 45 sales of securities—available-for-sale during the nine months ended September 30, 2019, which resulted in a net loss of $28,000. There were no securities—available-for-sale in a nonaccrual status at September 30, 2020 or December 31, 2019.

There were no sales of securities—held-to-maturity during the nine months ended September 30, 2020 or 2019, although there were partial calls of securities that resulted in a net loss of $1,000 for the nine months ended September 30, 2019. There were no securities—held-to-maturity in a nonaccrual status or 30 days or more past due at September 30, 2020 or December 31, 2019.

The Company also sold Visa Class B stock during the nine months ended September 30, 2020, with a net gain of $519,000. The stock was previously carried at a zero-cost basis due to transfer restrictions and uncertainty of litigation.

The amortized cost and estimated fair value of securities at September 30, 2020, by contractual maturity, are shown below (in thousands). Expected maturities will differ from contractual maturities because some securities may be called or prepaid with or without call or prepayment penalties.


	September 30, 2020
	Trading				Available-for-Sale				Held-to-Maturity
	Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value
Maturing in one year or less	$	—	$	—	$	—	$	—	$	—	$	—
Maturing after one year through five years	—		—		60,411		62,725		57,360		59,541
Maturing after five years through ten years	—		—		478,140		500,140		40,458		42,822
Maturing after ten years through twenty years	27,203		23,276		446,834		463,236		118,611		123,188
Maturing after twenty years	—		—		704,684		732,283		212,706		225,255


	$	27,203	$	23,276	$	1,690,069	$	1,758,384	$	429,135	$	450,806

The following table presents, as of September 30, 2020, investment securities which were pledged to secure borrowings, public deposits or other obligations as permitted or required by law (in thousands):


	September 30, 2020
	Carrying Value		Amortized Cost		Fair Value
Purpose or beneficiary:
State and local governments public deposits	$	152,148	$	151,455	$	161,497
Interest rate swap counterparties	29,623		28,473		29,849
Repurchase agreements	204,034		194,374		204,034
Other	2,627		2,627		2,707
Total pledged securities	$	388,432	$	376,929	$	398,087

The Company monitors the credit quality of held-to-maturity debt securities through the use of credit rating. Credit ratings are reviewed and updated quarterly. The following table summarizes the amortized cost of held-to-maturity debt securities by credit rating at September 30, 2020 (in thousands):


	September 30, 2020
	U.S. Government and agency obligations		Municipal bonds		Corporate bonds		Mortgage-backed or related securities		Total
AAA/AA/A	$	—	$	353,648	$	500	$	—	$	354,148

Not Rated	341		23,371		2,754		48,521		74,987


	$	341	$	377,019	$	3,254	$	48,521	$	429,135

The following table presents the activity in the allowance for credit losses for held-to-maturity debt securities by major type for the three and nine months ended September 30, 2020 (in thousands):


	For the Three Months Ended September 30, 2020
	U.S. Government and agency obligations		Municipal bonds		Corporate bonds		Mortgage-backed or related securities		Total
Allowance for credit losses - securities
Beginning Balance	$	—	$	61	$	41	$	—	$	102

(Recapture)/Provision for credit losses	—		(1)		1		—		—



Ending Balance	$	—	$	60	$	42	$	—	$	102