Securities (Tables)

12 Months Ended

Dec. 31, 2022

Investments, Debt and Equity Securities [Abstract]

Book Values and Fair Values of Available-for-Sale Securities

The book values and approximate fair values of investment securities at December 31, 2022 and 2021 are summarized as follows:

	2022					2021
	Amortized Cost		Fair Value	Unrealized		Amortized Cost	Fair Value	Unrealized
($ in thousands)				Gains	(Losses)			Gains	(Losses)
Securities available for sale:
US Treasury securities	$	174,420	168,758	—	(5,662)	—	—	—	—
Government-sponsored enterprise securities	71,957		57,456	—	(14,501)	71,951	69,179	—	(2,772)
Mortgage-backed securities	2,467,839		2,045,000	4	(422,843)	2,545,150	2,514,805	9,489	(39,834)
Corporate bonds	44,340		43,279	—	(1,061)	45,380	46,430	1,106	(56)
Total available for sale	$	2,758,556	2,314,493	4	(444,067)	2,662,481	2,630,414	10,595	(42,662)
Securities held to maturity:
Mortgage-backed securities	$	15,150	14,221	—	(929)	20,260	20,845	585	—
State and local governments	526,550		418,307	7	(108,250)	493,565	490,854	2,955	(5,666)
Total held to maturity	$	541,700	432,528	7	(109,179)	513,825	511,699	3,540	(5,666)

Book Values and Fair Values of Held-to-Maturity Securities

The book values and approximate fair values of investment securities at December 31, 2022 and 2021 are summarized as follows:

	2022					2021
	Amortized Cost		Fair Value	Unrealized		Amortized Cost	Fair Value	Unrealized
($ in thousands)				Gains	(Losses)			Gains	(Losses)
Securities available for sale:
US Treasury securities	$	174,420	168,758	—	(5,662)	—	—	—	—
Government-sponsored enterprise securities	71,957		57,456	—	(14,501)	71,951	69,179	—	(2,772)
Mortgage-backed securities	2,467,839		2,045,000	4	(422,843)	2,545,150	2,514,805	9,489	(39,834)
Corporate bonds	44,340		43,279	—	(1,061)	45,380	46,430	1,106	(56)
Total available for sale	$	2,758,556	2,314,493	4	(444,067)	2,662,481	2,630,414	10,595	(42,662)
Securities held to maturity:
Mortgage-backed securities	$	15,150	14,221	—	(929)	20,260	20,845	585	—
State and local governments	526,550		418,307	7	(108,250)	493,565	490,854	2,955	(5,666)
Total held to maturity	$	541,700	432,528	7	(109,179)	513,825	511,699	3,540	(5,666)

Schedule of Information Regarding Securities with Unrealized Losses

The following table presents information regarding securities with unrealized losses at December 31, 2022:

	Securities in an Unrealized Loss Position for Less than 12 Months			Securities in an Unrealized Loss Position for More than 12 Months		Total
($ in thousands)	Fair Value		Unrealized Losses	Fair Value	Unrealized Losses	Fair Value	Unrealized Losses
US Treasury securities	$	168,758	5,662	—	—	168,758	5,662
Government-sponsored enterprise securities	—		—	57,456	14,501	57,456	14,501
Mortgage-backed securities	221,006		18,215	1,835,958	405,557	2,056,964	423,772
Corporate bonds	40,644		947	886	114	41,530	1,061
State and local governments	48,385		8,323	368,897	99,927	417,282	108,250
Total temporarily impaired securities	$	478,793	33,147	2,263,197	520,099	2,741,990	553,246

The following table presents information regarding securities with unrealized losses at December 31, 2021:

	Securities in an Unrealized Loss Position for Less than 12 Months			Securities in an Unrealized Loss Position for More than 12 Months		Total
($ in thousands)	Fair Value		Unrealized Losses	Fair Value	Unrealized Losses	Fair Value	Unrealized Losses
Government-sponsored enterprise securities	$	21,436	522	47,743	2,250	69,179	2,772
Mortgage-backed securities	1,773,022		25,977	404,484	13,857	2,177,506	39,834
Corporate bonds	999		1	945	55	1,944	56
State and local governments	228,279		3,797	34,398	1,869	262,677	5,666
Total temporarily impaired securities	$	2,023,736	30,297	487,570	18,031	2,511,306	48,328

Schedule of Book Values and Approximate Fair Values of Investment Securities by Contractual Maturity

The book values and approximate fair values of investment securities at December 31, 2022, by contractual maturity, are summarized in the table below. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties.

	Securities Available for Sale			Securities Held to Maturity
($ in thousands)	Amortized Cost		Fair Value	Amortized Cost	Fair Value
Debt securities
Due within one year	$	25,078	25,036	—	—
Due after one year but within five years	176,932		171,224	997	873
Due after five years but within ten years	87,707		72,348	61,509	50,726
Due after ten years	1,000		885	464,044	366,708
Mortgage-backed securities	2,467,839		2,045,000	15,150	14,221
Total securities	$	2,758,556	2,314,493	541,700	432,528