Investment Securities (Tables)

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Approximate Market Value of Securities

The amortized cost, gross unrealized gains, gross unrealized losses and approximate market value of the Corporation's investment securities at the dates indicated were:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Available for sale at December 31, 2019
U.S. Government-sponsored agency securities	$	38,529	$	346	$	—	$	38,875
State and municipal	859,511		41,092		807		899,796
U.S. Government-sponsored mortgage-backed securities	842,349		10,378		1,404		851,323
Corporate obligations	31		—		—		31
Total available for sale	1,740,420		51,816		2,211		1,790,025
Held to maturity at December 31, 2019
U.S. Government-sponsored agency securities	15,619		1		37		15,583
State and municipal	354,115		15,151		107		369,159
U.S. Government-sponsored mortgage-backed securities	434,804		6,921		401		441,324
Foreign investment	1,500		—		—		1,500
Total held to maturity	806,038		22,073		545		827,566
Total Investment Securities	$	2,546,458	$	73,889	$	2,756	$	2,617,591
Available for sale at December 31, 2018
U.S. Government-sponsored agency securities	$	13,493	$	92	$	3	$	13,582
State and municipal	605,994		5,995		5,854		606,135
U.S. Government-sponsored mortgage-backed securities	530,209		634		8,396		522,447
Corporate obligations	31		—		—		31
Total available for sale	1,149,727		6,721		14,253		1,142,195
Held to maturity at December 31, 2018
U.S. Government-sponsored agency securities	22,618		—		545		22,073
State and municipal	197,909		2,858		872		199,895
U.S. Government-sponsored mortgage-backed securities	268,860		713		3,323		266,250
Foreign investment	1,000		—		1		999
Total held to maturity	490,387		3,571		4,741		489,217
Total Investment Securities	$	1,640,114	$	10,292	$	18,994	$	1,631,412

Investments' Gross Unrealized Losses and Fair Value Aggregated by Investment Category and Length of Time in Continuous Unrealized Loss Position

The following table shows the Corporation’s gross unrealized losses and fair value, aggregated by investment category and length of time the individual securities have been in a continuous unrealized loss position at December 31, 2019 and 2018: 

	Less than 12 Months				12 Months or Longer				Total
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Temporarily Impaired Available for Sale Securities at December 31, 2019
State and municipal	$	76,273	$	807	$	—	$	—	$	76,273	$	807
U.S. Government-sponsored mortgage-backed securities	127,673		1,326		20,796		78		148,469		1,404
Total Temporarily Impaired Available for Sale Securities	203,946		2,133		20,796		78		224,742		2,211
Temporarily Impaired Held to Maturity Securities at December 31, 2019
U.S. Government-sponsored agency securities	3,016		4		12,467		33		15,483		37
State and municipal	22,947		107		—		—		22,947		107
U.S. Government-sponsored mortgage-backed securities	124,253		364		7,991		37		132,244		401
Total Temporarily Impaired Held to Maturity Securities	150,216		475		20,458		70		$	170,674	545
Total Temporarily Impaired Investment Securities	$	354,162	$	2,608	$	41,254	$	148	$	395,416	$	2,756
	Less than 12 Months				12 Months or Longer				Total
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Temporarily Impaired Available for Sale Securities at December 31, 2018
U.S. Government-sponsored agency securities	$	1,490	$	3	$	—	$	—	$	1,490	$	3
State and municipal	234,431		3,958		38,028		1,896		272,459		5,854
U.S. Government-sponsored mortgage-backed securities	196,601		2,400		217,121		5,996		413,722		8,396
Total Temporarily Impaired Available for Sale Securities	432,522		6,361		255,149		7,892		687,671		14,253
Temporarily Impaired Held to Maturity Securities at December 31, 2018
U.S. Government-sponsored agency securities	—		—		22,073		545		22,073		545
State and municipal	14,952		369		16,786		503		31,738		872
U.S. Government-sponsored mortgage-backed securities	102,828		876		87,268		2,447		190,096		3,323
Foreign investment	—		—		999		1		999		1
Total Temporarily Impaired Held to Maturity Securities	117,780		1,245		127,126		3,496		244,906		4,741
Total Temporarily Impaired Investment Securities	$	550,302	$	7,606	$	382,275	$	11,388	$	932,577	$	18,994

Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity

Expected maturities will differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties.

	Available for Sale				Held to Maturity
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Maturity Distribution at December 31, 2019
Due in one year or less	$	1,134	$	1,136	$	9,920	$	10,105
Due after one through five years	5,031		5,141		45,197		45,654
Due after five through ten years	74,745		76,920		84,153		88,844
Due after ten years	817,161		855,505		231,964		241,639
	898,071		938,702		371,234		386,242
U.S. Government-sponsored mortgage-backed securities	842,349		851,323		434,804		441,324
Total Investment Securities	$	1,740,420	$	1,790,025	$	806,038	$	827,566

Schedule of Gross Gains on Sales and Redemptions of Available for Sale Securities

Gross gains and losses on the sales and redemptions of available for sale securities for the for the years indicated are shown below.

	2019		2018		2017
Sales and Redemptions of Available for Sale Securities:
Gross gains	$	4,415	$	4,269	$	2,681
Gross losses	—		—		50