INVESTMENT SECURITIES

The following is a summary of the amortized cost and fair value of investment securities available-for-sale and investment securities held-to-maturity at December 31, 2015 and 2014:



	Investment Securities Available-for-Sale
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
	(In thousands)
December 31, 2015
U.S. Treasury securities	$	5,773	$	—	$	8	$	5,765
Government sponsored agencies	195,711		78		800		194,989
State and political subdivisions	14,731		395		6		15,120
Residential mortgage-backed securities	189,452		538		2,222		187,768
Collateralized mortgage obligations	133,256		111		1,137		132,230
Corporate bonds	14,825		2		200		14,627
Preferred stock and trust preferred securities	2,888		344		—		3,232
Total	$	556,636	$	1,468	$	4,373	$	553,731
December 31, 2014
U.S. Treasury securities	$	8,272	$	—	$	13	$	8,259
Government sponsored agencies	263,658		356		511		263,503
State and political subdivisions	45,157		1,087		17		46,227
Residential mortgage-backed securities	240,465		885		1,543		239,807
Collateralized mortgage obligations	145,316		261		1,194		144,383
Corporate bonds	44,930		213		48		45,095
Preferred stock	1,389		201		—		1,590
Total	$	749,187	$	3,003	$	3,326	$	748,864



	Investment Securities Held-to-Maturity
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
	(In thousands)
December 31, 2015
State and political subdivisions	$	509,471	$	7,446	$	4,512	$	512,405
Trust preferred securities	500		—		200		300
Total	$	509,971	$	7,446	$	4,712	$	512,705
December 31, 2014
State and political subdivisions	$	305,913	$	7,294	$	4,557	$	308,650
Trust preferred securities	10,500		—		3,410		7,090
Total	$	316,413	$	7,294	$	7,967	$	315,740

The majority of the Corporation's residential mortgage-backed securities and collateralized mortgage obligations are backed by a U.S. government agency (Government National Mortgage Association) or a government sponsored enterprise (Federal Home Loan Mortgage Corporation or Federal National Mortgage Association).

At December 31, 2014, the Corporation held a $10.5 million trust preferred investment security that had been issued by Lake Michigan. With the acquisition of Lake Michigan, this investment was settled as of the acquisition date at par.

The following is a summary of the amortized cost and fair value of investment securities at December 31, 2015, by maturity, for both available-for-sale and held-to-maturity investment securities. The maturities of residential mortgage-backed securities and collateralized mortgage obligations are based on scheduled principal payments. The maturities of all other debt securities are based on final contractual maturity.



	December 31, 2015
	Amortized Cost		Fair Value
	(In thousands)
Investment Securities Available-for-Sale:
Due in one year or less	$	170,838	$	170,098
Due after one year through five years	326,018		324,187
Due after five years through ten years	53,317		52,649
Due after ten years	5,074		5,064
Preferred stock	1,389		1,733
Total	$	556,636	$	553,731
Investment Securities Held-to-Maturity:
Due in one year or less	$	59,834	$	59,938
Due after one year through five years	236,141		236,491
Due after five years through ten years	136,383		137,188
Due after ten years	77,613		79,088
Total	$	509,971	$	512,705

The following schedule summarizes information for both available-for-sale and held-to-maturity investment securities with gross unrealized losses at December 31, 2015 and 2014, aggregated by category and length of time that individual securities have been in a continuous unrealized loss position.



	Less Than 12 Months				12 Months or More				Total
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
December 31, 2015
U.S. Treasury securities	$	5,765	$	8	$	—	$	—	$	5,765	$	8
Government sponsored agencies	114,640		292		21,681		508		136,321		800
State and political subdivisions	195,285		2,891		68,361		1,627		263,646		4,518
Residential mortgage-backed securities	169,226		2,146		3,435		76		172,661		2,222
Collateralized mortgage obligations	60,459		408		39,382		729		99,841		1,137
Corporate bonds	9,532		200		—		—		9,532		200
Trust preferred securities	—		—		300		200		300		200
Total	$	554,907	$	5,945	$	133,159	$	3,140	$	688,066	$	9,085
December 31, 2014
U.S. Treasury securities	$	8,259	$	13	$	—	$	—	$	8,259	$	13
Government sponsored agencies	166,963		406		31,927		105		198,890		511
State and political subdivisions	62,310		3,348		36,847		1,226		99,157		4,574
Residential mortgage-backed securities	17,276		52		180,194		1,491		197,470		1,543
Collateralized mortgage obligations	63,077		179		31,620		1,015		94,697		1,194
Corporate bonds	—		—		14,952		48		14,952		48
Trust preferred securities	—		—		7,090		3,410		7,090		3,410
Total	$	317,885	$	3,998	$	302,630	$	7,295	$	620,515	$	11,293

An assessment is performed quarterly by the Corporation to determine whether unrealized losses in its investment securities portfolio are temporary or other-than-temporary by carefully considering all reasonably available information. The Corporation reviews factors such as financial statements, credit ratings, news releases and other pertinent information of the underlying issuer or company to make its determination. Management did not believe any individual unrealized loss on any investment security at December 31, 2015, represented an other-than-temporary impairment (OTTI). Management believed that the unrealized losses on investment securities at December 31, 2015 were temporary in nature and due primarily to changes in interest rates and reduced market liquidity and not as a result of credit-related issues.

At December 31, 2015, the Corporation did not have the intent to sell any of its impaired investment securities and believed that it was more-likely-than-not that the Corporation will not have to sell any such investment securities before a full recovery of amortized cost. Accordingly, at December 31, 2015, the Corporation believed the impairments in its investment securities portfolio were temporary in nature. However, there is no assurance that OTTI may not occur in the future.

Investment securities with an amortized cost of $516 million and $493 million at December 31, 2015 and 2014, respectively, were pledged to secure public fund deposits, short-term borrowings and for other purposes as required by law.