Investment Securities (Tables)

9 Months Ended

Sep. 30, 2021

Investments, Debt and Equity Securities [Abstract]

Schedule of investment securities available-for-sale

The following table shows investment securities available-for-sale.

(Dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
September 30, 2021
U.S. Treasury and Federal agencies securities	$	893,378	$	5,192	$	(4,898)	$	893,672
U.S. States and political subdivisions securities	93,764		1,537		(751)		94,550
Mortgage-backed securities — Federal agencies	569,805		7,140		(5,795)		571,150
Corporate debt securities	22,509		759		—		23,268
Foreign government and other securities	600		—		—		600
Total debt securities available-for-sale	$	1,580,056	$	14,628	$	(11,444)	$	1,583,240
December 31, 2020
U.S. Treasury and Federal agencies securities	$	610,195	$	9,521	$	(234)	$	619,482
U.S. States and political subdivisions securities	78,812		2,346		(31)		81,127
Mortgage-backed securities — Federal agencies	442,748		11,237		(196)		453,789
Corporate debt securities	40,813		1,556		—		42,369
Foreign government and other securities	700		—		—		700
Total debt securities available-for-sale	$	1,173,268	$	24,660	$	(461)	$	1,197,467

Schedule of contractual maturities of investments in debt securities available-for-sale

The following table shows the contractual maturities of investments in debt securities available-for-sale at September 30, 2021. Expected maturities will differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

(Dollars in thousands)	Amortized Cost		Fair Value
Due in one year or less	$	127,657	$	128,770
Due after one year through five years	752,143		754,188
Due after five years through ten years	129,981		128,687
Due after ten years	470		445
Mortgage-backed securities	569,805		571,150
Total debt securities available-for-sale	$	1,580,056	$	1,583,240

Schedule of gross unrealized losses and fair value by investment category and age

The following table summarizes gross unrealized losses and fair value by investment category and age. At September 30, 2021, the Company’s available-for-sale securities portfolio consisted of 679 securities, 218 of which were in an unrealized loss position.

	Less than 12 Months				12 months or Longer				Total
(Dollars in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
September 30, 2021
U.S. Treasury and Federal agencies securities	$	562,067	$	(4,100)	$	47,727	$	(798)	$	609,794	$	(4,898)
U.S. States and political subdivisions securities	38,980		(729)		418		(22)		39,398		(751)
Mortgage-backed securities - Federal agencies	346,008		(5,791)		344		(4)		346,352		(5,795)
Corporate debt securities	—		—		—		—		—		—
Foreign government and other securities	600		—		—		—		600		—
Total debt securities available-for-sale	$	947,655	$	(10,620)	$	48,489	$	(824)	$	996,144	$	(11,444)
December 31, 2020
U.S. Treasury and Federal agencies securities	$	136,534	$	(234)	$	—	$	—	$	136,534	$	(234)
U.S. States and political subdivisions securities	6,391		(30)		199		(1)		6,590		(31)
Mortgage-backed securities - Federal agencies	67,736		(187)		3,274		(9)		71,010		(196)
Corporate debt securities	—		—		—		—		—		—
Foreign government and other securities	200		—		—		—		200		—
Total debt securities available-for-sale	$	210,861	$	(451)	$	3,473	$	(10)	$	214,334	$	(461)

Schedule of gross realized gains and losses from securities available-for-sale portfolio

The following table shows the gross realized gains and losses from the available-for-sale debt securities portfolio. Realized gains and losses of all securities are computed using the specific identification cost basis.

	Three Months Ended September 30,				Nine Months Ended September 30,
(Dollars in thousands)	2021		2020		2021		2020
Gross realized gains	$	—	$	—	$	221	$	285
Gross realized losses	—		—		(901)		(6)
Net realized (losses) gains	$	—	$	—	$	(680)	$	279