Investment Securities Available-for-Sale (Tables)

6 Months Ended

Jun. 30, 2021

Investments, Debt and Equity Securities [Abstract]

Schedule of amortized cost and estimated fair value of securities available-for-sale

Amortized cost and estimated fair value of securities available-for-sale are summarized as follows:

			Gross		Gross		Allowance		Estimated
June 30, 2021	Amortized		Unrealized		Unrealized		for Credit		Fair
(dollars in thousands)	Cost		Gains		Losses		Losses		Value
U.S. agency securities	$	359,339	$	1,539	$	(3,567)	$	—	$	357,311
Residential mortgage backed securities	1,143,931		9,944		(7,553)		—		1,146,322
Municipal bonds	95,444		4,925		(90)		(2)		100,277
Corporate bonds	75,550		1,741		(239)		(130)		76,922
	$	1,674,264	$	18,149	$	(11,449)	$	(132)	$	1,680,832

			Gross		Gross				Estimated
December 31, 2020	Amortized		Unrealized		Unrealized		Allowance for		Fair
(dollars in thousands)	Cost		Gains		Losses		Credit Losses		Value
U.S. agency securities	$	181,087	$	1,461	$	(627)	$	—	$	181,921
Residential mortgage backed securities	811,328		14,506		(833)		—		825,001
Municipal bonds	102,259		5,872		—		(18)		108,113
Corporate bonds	34,383		1,624		(8)		(149)		35,850
	$	1,129,057	$	23,463	$	(1,468)	$	(167)	$	1,150,885

Schedule of gross unrealized losses and fair value by length of time that the individual available-for-sale securities have been in a continuous unrealized loss

Gross unrealized losses and fair value of available-for-sale securities for which an allowance for credit losses has not been recorded, by length of time that individual securities have been in a continuous unrealized loss position are as follows:

		Less than				12 Months
		12 Months				or Greater				Total
		Estimated				Estimated				Estimated
June 30, 2021	Number of	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(dollars in thousands)	Securities	Value		Losses		Value		Losses		Value		Losses
U. S. agency securities	45	$	198,756	$	3,085	$	43,126	$	482	$	241,882	$	3,567
Residential mortgage backed securities	94	693,251		7,500		5,158		53		698,409		7,553
Corporate bonds	4	21,375		239		—		—		21,375		239
Municipal bonds	3	12,532		90		—		—		12,532		90
	146	$	925,914	$	10,914	$	48,284	$	535	$	974,198	$	11,449

		Less than				12 Months
		12 Months				or Greater				Total
		Estimated				Estimated				Estimated
December 31, 2020	Number of	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(dollars in thousands)	Securities	Value		Losses		Value		Losses		Value		Losses
U. S. agency securities	28	$	46,412	$	67	$	41,320	$	560	$	87,732	$	627
Residential mortgage backed securities	35	170,178		782		6,419		51		176,597		833
Corporate bonds	3	5,764		8		—		—		5,764		8
	66	$	222,354	$	857	$	47,739	$	611	$	270,093	$	1,468

Schedule of amortized cost and estimated fair value of investments available-for-sale by contractual maturity

or residential mortgage backed securities (“MBS”) are not shown as they may differ significantly from expected maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

	June 30, 2021				December 31, 2020
	Amortized		Estimated		Amortized		Estimated
(dollars in thousands)	Cost		Fair Value		Cost		Fair Value
U. S. agency securities maturing:
One year or less	$	159,698	$	158,781	$	53,916	$	53,906
After one year through five years	122,900		122,872		110,083		110,777
Five years through ten years	76,741		75,658		17,087		17,240
Residential mortgage backed securities	1,143,931		1,146,322		811,328		825,001
Municipal bonds maturing:
One year or less	2,764		2,796		4,329		4,348
After one year through five years	26,121		27,751		26,622		28,272
Five years through ten years	66,559		69,732		69,309		73,389
After ten years	—		—		2,000		2,121
Corporate bonds maturing:
One year or less	6,314		6,542		5,218		5,220
After one year through five years	48,958		49,744		22,189		23,267
Five years through ten years	20,278		20,766		—		—
After ten years	—		—		6,976		7,511
Allowance for Credit Losses	—		(132)		—		(167)
	$	1,674,264	$	1,680,832	$	1,129,057	$	1,150,885