Securities (Tables)

6 Months Ended

Jun. 30, 2020

Securities Available for Sale

This table provides detailed information about securities available for sale at June 30, 2020 and December 31, 2019 (in thousands):

June 30, 2020	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasury	$	29,904	$	1,016	$	—		$	30,920
U.S. Agencies		413,537		7,065		(50	)		420,552
Mortgage-backed		4,549,567		200,261		(371	)		4,749,457
State and political subdivisions		3,066,713		156,257		(336	)		3,222,634
Corporates		56,752		3,309		—			60,061
Total	$	8,116,473	$	367,908	$	(757	)	$	8,483,624

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 June 30, 2020 and December 31, 2019 (in thousands):

	Less than 12 months							12 months or more							Total
June 30, 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		12		314,609		(50	)		—		—		—			12		314,609		(50	)
Mortgage-backed		14		80,375		(371	)		—		—		—			14		80,375		(371	)
State and political subdivisions		43		43,573		(331	)		3		1,060		(5	)		46		44,633		(336	)
Corporates		—		—		—			—		—		—			—		—		—
Total		69	$	438,557	$	(752	)		3	$	1,060	$	(5	)		72	$	439,617	$	(757	)

	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 June 30, 2020 and December 31, 2019, respectively (in thousands):

	Less than 12 months					12 months or more					Total
June 30, 2020	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
State and political subdivisions	$	75,383	$	(1,974	)	$	106,510	$	(7,825	)	$	181,893	$	(9,799	)
Total	$	75,383	$	(1,974	)	$	106,510	$	(7,825	)	$	181,893	$	(9,799	)

	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 June 30, 2020 (in thousands):

	Amortized Cost Basis by Credit Rating - HTM Debt Securities
June 30, 2020	AA		A		BBB		BB		B		CCC-C		Total
State and political subdivisions:
Competitive	$	8,998	$	362,821	$	614,675	$	23,364	$	—	$	12,561	$	1,022,419
Utilities		—		57,345		35,166		—		—		—		92,511
Total state and political subdivisions	$	8,998	$	420,166	$	649,841	$	23,364	$	—	$	12,561	$	1,114,930

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 June 30, 2020 and December 31, 2019 (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
June 30, 2020	Cost		Gains		Losses			Value
FRB and FHLB stock	$	33,252	$	—	$	—		$	33,252
Other securities – non-marketable		117,894		3,270		(210	)		120,954
Total Other securities	$	151,146	$	3,270	$	(210	)	$	154,206
			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 June 30, 2020 (in thousands):

	Amortized		Fair
	Cost		Value
Due in 1 year or less	$	210,489	$	211,619
Due after 1 year through 5 years		1,009,733		1,030,371
Due after 5 years through 10 years		578,083		604,505
Due after 10 years		1,768,601		1,887,672
Total		3,566,906		3,734,167
Mortgage-backed securities		4,549,567		4,749,457
Total securities available for sale	$	8,116,473	$	8,483,624

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 June 30, 2020 and December 31, 2019, respectively (in thousands):

				Gross		Gross
	Amortized			Unrealized		Unrealized			Fair
June 30, 2020	Cost			Gains		Losses			Value
State and political subdivisions:
Due in 1 year or less	$	670		$	11	$	—		$	681
Due after 1 year through 5 years		125,326			4,251		(127	)		129,450
Due after 5 years through 10 years		437,943			17,035		(457	)		454,521
Due after 10 years		550,991			27,405		(9,215	)		569,181
Total state and political subdivisions	$	1,114,930		$	48,702	$	(9,799	)	$	1,153,833
Allowance for credit losses		(3,305	)
Total state and political subdivisions, net of allowance for credit losses	$	1,111,625

			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