Securities (Tables)

3 Months Ended

Mar. 31, 2020

Securities Available for Sale

This table provides detailed information about securities available for sale at March 31, 2020 and December 31, 2019 (in thousands):

March 31, 2020	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury	$	30,549	$	1,056	$	—		$	31,605
U.S. Agencies		94,195		6,421		—			100,616
Mortgage-backed		4,067,786		171,441		(4,578	)		4,234,649
State and political subdivisions		2,980,676		114,292		(1,276	)		3,093,692
Corporates		179,974		1,368		(2,453	)		178,889
Total	$	7,353,180	$	294,578	$	(8,307	)	$	7,639,451

December 31, 2019	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury	$	63,835	$	408	$	(165	)	$	64,078
U.S. Agencies		89,867		3,154		—			93,021
Mortgage-backed		4,030,688		58,184		(17,078	)		4,071,794
State and political subdivisions		2,954,276		78,867		(3,226	)		3,029,917
Corporates		185,314		3,259		(21	)		188,552
Total	$	7,323,980	$	143,872	$	(20,490	)	$	7,447,362

Gross Unrealized Losses and Fair Value of Investment Securities Available for Sale

The following table shows the Company’s available for sale investments’ gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at March 31, 2020 and December 31, 2019 (in thousands):

	Less than 12 months							12 months or more							Total
March 31, 2020	Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses			Count		Fair Value		Unrealized Losses
Description of Securities
U.S. Treasury		—	$	—	$	—			—	$	—	$	—			—	$	—	$	—
U.S. Agencies		1		4,406		—			—		—		—			1		4,406		—
Mortgage-backed		36		159,593		(4,079	)		10		34,227		(499	)		46		193,820		(4,578	)
State and political subdivisions		184		127,235		(1,267	)		4		1,158		(9	)		188		128,393		(1,276	)
Corporates		63		96,594		(2,453	)		—		—		—			63		96,594		(2,453	)
Total		284	$	387,828	$	(7,799	)		14	$	35,385	$	(508	)		298	$	423,213	$	(8,307	)

	Less than 12 months					12 months or more					Total
December 31, 2019	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Description of Securities
U.S. Treasury	$	—	$	—		$	19,863	$	(165	)	$	19,863	$	(165	)
U.S. Agencies		—		—			—		—			—		—
Mortgage-backed		947,415		(5,236	)		517,824		(11,842	)		1,465,239		(17,078	)
State and political subdivisions		361,440		(3,084	)		27,501		(142	)		388,941		(3,226	)
Corporates		13,685		(21	)		—		—			13,685		(21	)
Total	$	1,322,540	$	(8,341	)	$	565,188	$	(12,149	)	$	1,887,728	$	(20,490	)

Gross Unrealized Losses and Fair Value of Investment Securities Held to Maturity

The following table shows the Company’s held to maturity investments’ gross unrealized losses and fair value, aggregated by length of time that individual securities have been in a continuous unrealized loss position, at March 31, 2020 and December 31, 2019, respectively (in thousands):

	Less than 12 months					12 months or more					Total
March 31, 2020	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
State and political subdivisions	$	20,357	$	(384	)	$	113,935	$	(3,436	)	$	134,292	$	(3,820	)
Total	$	20,357	$	(384	)	$	113,935	$	(3,436	)	$	134,292	$	(3,820	)

	Less than 12 months					12 months or more					Total
December 31, 2019	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
State and political subdivisions	$	471,544	$	(12,424	)	$	546,572	$	(22,595	)	$	1,018,116	$	(35,019	)
Total	$	471,544	$	(12,424	)	$	546,572	$	(22,595	)	$	1,018,116	$	(35,019	)

Schedule of Amortized Cost Basis by Credit Rating of Held to Maturity Investment

The following table shows the amortized cost basis by credit rating of the Company’s held to maturity investments at March 31, 2020 (in thousands):

	Amortized Cost Basis by Credit Rating - HTM Debt Securities
March 31, 2020	AA		A		BBB		BB		B		CCC-C		Total
State and political subdivisions:
Competitive	$	8,998	$	394,082	$	597,984	$	22,519	$	685	$	12,576	$	1,036,844
Utilities		—		57,349		19,967		—		—		—		77,316
Total state and political subdivisions	$	8,998	$	451,431	$	617,951	$	22,519	$	685	$	12,576	$	1,114,160

Schedule of Federal Reserve Bank Stock and Federal Home Loan Bank Stock and Other Securities

The table below provides detailed information for FRB stock and Federal Home Loan Bank (FHLB) stock and other securities at March 31, 2020 and December 31, 2019 (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
March 31, 2020	Cost		Gains		Losses			Value
FRB and FHLB stock	$	33,252	$	—	$	—		$	33,252
Other securities – non-marketable		99,543		2,428		(29	)		101,942
Total Other securities	$	132,795	$	2,428	$	(29	)	$	135,194
			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
December 31, 2019	Cost		Gains		Losses			Value
FRB and FHLB stock	$	33,262	$	—	$	—		$	33,262
Other securities – non-marketable		69,868		5,295		(5	)		75,158
Total Other securities	$	103,130	$	5,295	$	(5	)	$	108,420

Available-for-sale Securities [Member]

Contractual Maturity Information

The following table presents contractual maturity information for securities available for sale at March 31, 2020 (in thousands):

	Amortized		Fair
	Cost		Value
Due in 1 year or less	$	225,943	$	226,438
Due after 1 year through 5 years		842,108		852,880
Due after 5 years through 10 years		580,312		594,772
Due after 10 years		1,637,031		1,730,712
Total		3,285,394		3,404,802
Mortgage-backed securities		4,067,786		4,234,649
Total securities available for sale	$	7,353,180	$	7,639,451

Held-to-maturity Securities [Member]

Contractual Maturity Information

The following table shows the Company’s held to maturity investments’ amortized cost, fair value, and gross unrealized gains and losses at March 31, 2020 and December 31, 2019, respectively (in thousands):

				Gross		Gross
	Amortized			Unrealized		Unrealized			Fair
March 31, 2020	Cost			Gains		Losses			Value
State and political subdivisions:
Due in 1 year or less	$	14,151		$	20	$	—		$	14,171
Due after 1 year through 5 years		93,532			2,785		(135	)		96,182
Due after 5 years through 10 years		414,223			11,534		(760	)		424,997
Due after 10 years		592,254			22,230		(2,925	)		611,559
Total state and political subdivisions	$	1,114,160		$	36,569	$	(3,820	)	$	1,146,909
Allowance for credit losses		(3,235	)
Total state and political subdivisions, net of allowance for credit losses	$	1,110,925

			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
December 31, 2019	Cost		Gains		Losses			Value
State and political subdivisions:
Due in 1 year or less	$	15,323	$	5	$	(60	)	$	15,268
Due after 1 year through 5 years		100,623		374		(699	)		100,298
Due after 5 years through 10 years		394,591		389		(8,400	)		386,580
Due after 10 years		605,565		494		(25,860	)		580,199
Total state and political subdivisions	$	1,116,102	$	1,262	$	(35,019	)	$	1,082,345