Investment Securities (Tables)

12 Months Ended

Dec. 31, 2017

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, 2017
State and municipal	$	510,852	$	16,932	$	1,091	$	526,693
U.S. Government-sponsored mortgage-backed securities	473,325		964		3,423		470,866
Corporate obligations	31						31
Equity securities	2,357						2,357
Total available for sale	986,565		17,896		4,514		999,947
Held to maturity at December 31, 2017
U.S. Government-sponsored agency securities	22,618				435		22,183
State and municipal	235,594		6,295		244		241,645
U.S. Government-sponsored mortgage-backed securities	301,443		3,341		1,404		303,380
Foreign Investment	1,000						1,000
Total held to maturity	560,655		9,636		2,083		568,208
Total Investment Securities	$	1,547,220	$	27,532	$	6,597	$	1,568,155
Available for sale at December 31, 2016
U.S. Government-sponsored agency securities	$	100					$	100
State and municipal	360,779		$	8,443	$	5,564	363,658
U.S. Government-sponsored mortgage-backed securities	313,459		1,904		3,071		312,292
Corporate obligations	31						31
Equity securities	21,820				1,039		20,781
Total available for sale	696,189		10,347		9,674		696,862
Held to maturity at December 31, 2016
U.S. Government-sponsored agency securities	22,619				479		22,140
State and municipal	224,811		3,136		1,796		226,151
U.S. Government-sponsored mortgage-backed securities	360,213		4,956		1,527		363,642
Total held to maturity	607,643		8,092		3,802		611,933
Total Investment Securities	$	1,303,832	$	18,439	$	13,476	$	1,308,795

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, 2017 and 2016: 

	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, 2017
State and municipal	$	13,296	$	198	$	35,324	$	893	$	48,620	$	1,091
U.S. Government-sponsored mortgage-backed securities	182,755		1,520		68,667		1,903		251,422		3,423
Total Temporarily Impaired Available for Sale Securities	196,051		1,718		103,991		2,796		300,042		4,514
Temporarily Impaired Held to Maturity Securities at December 31, 2017
U.S. Government-sponsored agency securities	9,988		131		12,196		304		22,184		435
State and municipal	2,430		36		15,805		208		18,235		244
U.S. Government-sponsored mortgage-backed securities	62,508		485		43,078		919		105,586		1,404
Total Temporarily Impaired Held to Maturity Securities	74,926		652		71,079		1,431		146,005		2,083
Total Temporarily Impaired Investment Securities	$	270,977	$	2,370	$	175,070	$	4,227	$	446,047	$	6,597
	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, 2016
State and municipal	$	126,593	$	5,564					$	126,593	$	5,564
U.S. Government-sponsored mortgage-backed securities	185,544		3,071						185,544		3,071
Equity securities	18,765		1,039						18,765		1,039
Total Temporarily Impaired Available for Sale Securities	330,902		9,674						330,902		9,674
Temporarily Impaired Held to Maturity Securities at December 31, 2016
U.S. Government-sponsored agency securities	19,121		479						19,121		479
State and municipal	50,897		1,796						50,897		1,796
U.S. Government-sponsored mortgage-backed securities	109,377		1,527						109,377		1,527
Total Temporarily Impaired Held to Maturity Securities	179,395		3,802						179,395		3,802
Total Temporarily Impaired Investment Securities	$	510,297	$	13,476					$	510,297	$	13,476

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, 2017
Due in one year or less	$	425	$	425	$	12,015	$	12,158
Due after one through five years	5,040		5,204		76,146		76,334
Due after five through ten years	74,921		78,806		54,441		55,679
Due after ten years	430,497		442,289		116,610		120,657
	510,883		526,724		259,212		264,828
U.S. Government-sponsored mortgage-backed securities	473,325		470,866		301,443		303,380
Equity securities	2,357		2,357
Total Investment Securities	$	986,565	$	999,947	$	560,655	$	568,208