SECURITIES (Tables)

12 Months Ended

Dec. 31, 2017

This table provides detailed information about securities available for sale at December 31, 2017 and 2016 (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
2017	Cost		Gains		Losses			Value
U.S. Treasury	$	40,092	$	—	$	(1,449	)	$	38,643
U.S. Agencies		14,762		—		(10	)		14,752
Mortgage-backed		3,719,369		1,914		(72,040	)		3,649,243
State and political subdivisions		2,546,517		11,965		(15,809	)		2,542,673
Corporates		13,278		—		(12	)		13,266
Total	$	6,334,018	$	13,879	$	(89,320	)	$	6,258,577

			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
2016	Cost		Gains		Losses			Value
U.S. Treasury	$	95,315	$	37	$	(1,526	)	$	93,826
U.S. Agencies		198,158		67		(48	)		198,177
Mortgage-backed		3,773,090		7,069		(68,460	)		3,711,699
State and political subdivisions		2,425,155		7,391		(36,789	)		2,395,757
Corporates		66,997		5		(127	)		66,875
Total	$	6,558,715	$	14,569	$	(106,950	)	$	6,466,334

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 December 31, 2017 and 2016 (in thousands).

	Less than 12 months					12 months or more					Total
2017	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Description of Securities
U.S. Treasury	$	9,851	$	(64	)	$	28,792	$	(1,385	)	$	38,643	$	(1,449	)
U.S. Agencies		14,553		(10	)		—		—			14,553		(10	)
Mortgage-backed		1,990,006		(19,980	)		1,562,333		(52,060	)		3,552,339		(72,040	)
State and political subdivisions		1,076,930		(7,325	)		376,560		(8,484	)		1,453,490		(15,809	)
Corporates		13,266		(12	)		—		—			13,266		(12	)
Total temporarily-impaired debt securities available for sale	$	3,104,606	$	(27,391	)	$	1,967,685	$	(61,929	)	$	5,072,291	$	(89,320	)

	Less than 12 months					12 months or more					Total
2016	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Description of Securities
U.S. Treasury	$	48,678	$	(1,526	)	$	—	$	—		$	48,678	$	(1,526	)
U.S. Agencies		103,979		(34	)		9,989		(14	)		113,968		(48	)
Mortgage-backed		2,735,868		(55,035	)		269,637		(13,425	)		3,005,505		(68,460	)
State and political subdivisions		1,748,922		(36,639	)		8,565		(150	)		1,757,487		(36,789	)
Corporates		41,966		(90	)		17,982		(37	)		59,948		(127	)
Total temporarily-impaired debt securities available for sale	$	4,679,413	$	(93,324	)	$	306,173	$	(13,626	)	$	4,985,586	$	(106,950	)

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

The table below provides detailed information for Federal Reserve Bank stock and Federal Home Loan Bank stock and other securities at December 31, 2017 and 2016 (in thousands):

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
2017	Cost		Gains		Losses		Value
FRB and FHLB stock	$	33,262	$	—	$	—	$	33,262
Other securities – marketable		3		4,637		—		4,640
Other securities – non-marketable		26,606		1,389		—		27,995
Total Federal Reserve Bank stock and other	$	59,871	$	6,026	$	—	$	65,897

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
2016	Cost		Gains		Losses		Value
FRB and FHLB stock	$	33,262	$	—	$	—	$	33,262
Other securities – marketable		4		9,948		—		9,952
Other securities – non-marketable		24,272		820		—		25,092
Total Federal Reserve Bank stock and other	$	57,538	$	10,768	$	—	$	68,306

Available-for-sale Securities [Member]

Contractual Maturity Information

The following table presents contractual maturity information for securities available for sale at December 31, 2017 (in thousands):

	Amortized		Fair
	Cost		Value
Due in 1 year or less	$	288,991	$	288,776
Due after 1 year through 5 years		1,128,445		1,126,389
Due after 5 years through 10 years		834,047		832,221
Due after 10 years		363,166		361,948
Total		2,614,649		2,609,334
Mortgage-backed securities		3,719,369		3,649,243
Total securities available for sale	$	6,334,018	$	6,258,577

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 December 31, 2017 and net unrealized gains, aggregated by maturity category, at December 31, 2016, respectively (in thousands).

			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
2017	Cost		Gains		Losses			Value
State and political subdivisions:
Due in 1 year or less	$	2,275	$	3	$	(24	)	$	2,254
Due after 1 year through 5 years		100,648		3,111		(2,834	)		100,925
Due after 5 years through 10 years		372,234		5,006		(14,117	)		363,123
Due after 10 years		785,857		6,952		(51,664	)		741,145
Total state and political subdivisions	$	1,261,014	$	15,072	$	(68,639	)	$	1,207,447

			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
2016	Cost		Gains		Losses			Value
State and political subdivisions:
Due in 1 year or less	$	6,077	$	5	$	(947	)	$	5,135
Due after 1 year through 5 years		82,650		2,376		(1,474	)		83,552
Due after 5 years through 10 years		341,741		8,854		(3,021	)		347,574
Due after 10 years		685,464		15,717		(31,415	)		669,766
Total state and political subdivisions	$	1,115,932	$	26,952	$	(36,857	)	$	1,106,027

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

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