Investment Securities (Tables)

3 Months Ended

Mar. 31, 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
March 31, 2021
U.S. Treasury and Federal agencies securities	$	675,940	$	7,482	$	(5,017)	$	678,405
U.S. States and political subdivisions securities	84,472		1,926		(729)		85,669
Mortgage-backed securities — Federal agencies	484,888		9,008		(4,406)		489,490
Corporate debt securities	35,800		1,276		—		37,076
Foreign government and other securities	700		—		—		700
Total debt securities available-for-sale	$	1,281,800	$	19,692	$	(10,152)	$	1,291,340
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 March 31, 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	$	96,850	$	97,884
Due after one year through five years	586,850		592,948
Due after five years through ten years	112,742		110,586
Due after ten years	470		432
Mortgage-backed securities	484,888		489,490
Total debt securities available-for-sale	$	1,281,800	$	1,291,340

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 March 31, 2021, the Company’s available-for-sale securities portfolio consisted of 646 securities, 152 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
March 31, 2021
U.S. Treasury and Federal agencies securities	$	368,296	$	(5,017)	$	—	$	—	$	368,296	$	(5,017)
U.S. States and political subdivisions securities	25,027		(696)		407		(33)		25,434		(729)
Mortgage-backed securities - Federal agencies	220,921		(4,398)		752		(8)		221,673		(4,406)
Corporate debt securities	—		—		—		—		—		—
Foreign government and other securities	—		—		—		—		—		—
Total debt securities available-for-sale	$	614,244	$	(10,111)	$	1,159	$	(41)	$	615,403	$	(10,152)
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 March 31,
(Dollars in thousands)	2021		2020
Gross realized gains	$	—	$	280
Gross realized losses	—		—
Net realized gains (losses)	$	—	$	280