Investment Securities (Tables)

6 Months Ended

Jun. 30, 2022

Investments, Debt and Equity Securities [Abstract]

Summary of Carrying Amounts of Securities and Their Approximate Fair Values

Investment securities have been classified in the unaudited consolidated balance sheets according to management’s intent. The carrying amounts of securities and their approximate fair values were as follows:

	June 30, 2022									December 31, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(dollars in thousands)
Available for sale securities
U.S. Government Sponsored    Enterprise obligations	$	22,997	$	—	$	(1,922	)	$	21,075	$	22,996	$	246	$	(231	)	$	23,011
Mortgage-backed securities		169,273		14		(18,157	)		151,130		176,531		959		(4,462	)		173,028
Corporate debt securities		1,744		9		(6	)		1,747		1,743		24		(3	)		1,764
Total available for sale securities	$	194,014	$	23	$	(20,085	)	$	173,952	$	201,270	$	1,229	$	(4,696	)	$	197,803
Held to maturity securities
Mortgage-backed securities	$	1,004,629	$	21	$	(107,309	)	$	897,341	$	864,983	$	3,981	$	(13,258	)	$	855,706
Corporate debt securities		2,749		1		(5	)		2,745		6,997		26		—			7,023
Municipal securities		98,480		307		(8,652	)		90,135		105,081		3,798		(516	)		108,363
Total held to maturity securities	$	1,105,858	$	329	$	(115,966	)	$	990,221	$	977,061	$	7,805	$	(13,774	)	$	971,092
Total	$	1,299,872	$	352	$	(136,051	)	$	1,164,173	$	1,178,331	$	9,034	$	(18,470	)	$	1,168,895

Gross Unrealized Losses of Aggregated by Investment Category and Length of Time that Individual Securities have been in Continuous Loss Position

The following tables show the Company’s securities with gross unrealized losses for which an allowance for credit losses has not been recorded at June 30, 2022 or at December 31, 2021, aggregated by investment category and length of time that individual securities have been in a continuous loss position:

	June 30, 2022
	Less than 12 months					12 months or longer					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(dollars in thousands)
Available for sale securities
U.S. Government Sponsored Enterprise    obligations	$	11,830	$	(1,170	)	$	9,245	$	(752	)	$	21,075	$	(1,922	)
Mortgage-backed securities		77,487		(4,768	)		73,190		(13,389	)		150,677		(18,157	)
Corporate debt securities		—		—			749		(6	)		749		(6	)
Total available for sale securities	$	89,317	$	(5,938	)	$	83,184	$	(14,147	)	$	172,501	$	(20,085	)
Held to maturity securities
Mortgage-backed securities	$	806,188	$	(91,491	)	$	88,138	$	(15,818	)	$	894,326	$	(107,309	)
Corporate debt securities		245		(5	)		—		—			245		(5	)
Municipal securities		45,807		(6,608	)		6,078		(2,044	)		51,885		(8,652	)
Total held to maturity securities	$	852,240	$	(98,104	)	$	94,216	$	(17,862	)	$	946,456	$	(115,966	)
Total	$	941,557	$	(104,042	)	$	177,400	$	(32,009	)	$	1,118,957	$	(136,051	)

	December 31, 2021
	Less than 12 months					12 months or longer					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(dollars in thousands)
Available for sale securities
U.S. Government Sponsored Enterprise    obligations	$	4,881	$	(115	)	$	4,884	$	(116	)	$	9,765	$	(231	)
Mortgage-backed securities		74,724		(2,253	)		47,871		(2,209	)		122,595		(4,462	)
Corporate debt securities		760		(3	)		—		—			760		(3	)
Total available for sale securities	$	80,365	$	(2,371	)	$	52,755	$	(2,325	)	$	133,120	$	(4,696	)
Held to maturity securities
Mortgage-backed securities	$	740,966	$	(12,509	)	$	15,345	$	(749	)	$	756,311	$	(13,258	)
Municipal securities		12,607		(194	)		5,716		(322	)		18,323		(516	)
Total held to maturity securities	$	753,573	$	(12,703	)	$	21,061	$	(1,071	)	$	774,634	$	(13,774	)
Total	$	833,938	$	(15,074	)	$	73,816	$	(3,396	)	$	907,754	$	(18,470	)

Schedule of Amortized Cost and Fair Value of Debt Securities, Aggregated By Earlier of Guaranteed Call Date or Contractual Maturity

The amortized cost and fair value of debt securities, aggregated by the earlier of call date or contractual maturity, are shown below. Maturities of mortgage-backed securities do not take into consideration scheduled amortization or prepayments. Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties.

	Within One Year				After One, But Within Five Years				After Five, But Within Ten Years				After Ten Years				Total
	Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value
At June 30, 2022	(dollars in thousands)
Available for sale securities
U.S. Government    Sponsored Enterprise    obligations	$	—	$	—	$	9,997	$	9,245	$	5,000	$	4,678	$	8,000	$	7,152	$	22,997	$	21,075
Mortgage-backed    securities		—		—		8,833		8,506		45,909		40,953		114,531		101,671		169,273		151,130
Corporate debt securities		1,744		1,747		—		—		—		—		—		—		1,744		1,747
Total available for    sale securities	$	1,744	$	1,747	$	18,830	$	17,751	$	50,909	$	45,631	$	122,531	$	108,823	$	194,014	$	173,952
Held to maturity securities
Mortgage-backed    securities	$	—	$	—	$	14,582	$	14,245	$	55,917	$	52,819	$	934,130	$	830,277	$	1,004,629	$	897,341
Corporate debt securities		2,499		2,500		250		245		—		—		—		—		2,749		2,745
Municipal securities		4,143		4,166		17,656		17,787		32,309		32,025		44,372		36,157		98,480		90,135
Total held to maturity    securities	$	6,642	$	6,666	$	32,488	$	32,277	$	88,226	$	84,844	$	978,502	$	866,434	$	1,105,858	$	990,221
Total	$	8,386	$	8,413	$	51,318	$	50,028	$	139,135	$	130,475	$	1,101,033	$	975,257	$	1,299,872	$	1,164,173

Summary of Credit Rating of Debt Securities Portfolio

The Company monitors the credit quality of certain debt securities through the use of credit ratings among other factors on a quarterly basis. The following tables summarize the credit rating of the Company’s debt securities portfolio at June 30, 2022 and December 31, 2021.

	June 30, 2022
	Mortgage-backed Securities (1)		Corporate Debt Securities		Municipal Securities		U.S. GSE Obligations		Total
	(dollars in thousands)
Available for sale securities, at fair value
AAA/AA/A	$	151,130	$	750	$	—	$	21,075	$	172,955
BBB/BB/B		—		997		—		—		997
Total available for sale securities	$	151,130	$	1,747	$	—	$	21,075	$	173,952
Held to maturity securities, at amortized cost
AAA/AA/A	$	1,004,629	$	2,749	$	98,480	$	—	$	1,105,858
Total held to maturity securities	$	1,004,629	$	2,749	$	98,480	$	—	$	1,105,858

	December 31, 2021
	Mortgage-backed Securities (1)		Corporate Debt Securities		Municipal Securities		U.S. GSE Obligations		Total
	(dollars in thousands)
Available for sale securities, at fair value
AAA/AA/A	$	173,028	$	759	$	—	$	23,011	$	196,798
BBB/BB/B		—		1,005		—		—		1,005
Total available for sale securities	$	173,028	$	1,764	$	—	$	23,011	$	197,803
Held to maturity securities, at amortized cost
AAA/AA/A	$	864,983	$	6,997	$	105,081	$	—	$	977,061
Total held to maturity securities	$	864,983	$	6,997	$	105,081	$	—	$	977,061

Includes agency mortgage-backed pass-through securities and collateralized mortgage obligations issued by U.S. Government Sponsored Enterprises ("GSEs") and U.S. government agencies, such as FNMA, FHLMC, and GNMA that are not rated by Moody’s or Standard & Poor's. Each security contains a guarantee by the issuing U.S. GSE or agency and therefore carries an implicit guarantee of the U.S. government. These have been categorized as AAA/AA/A.