Investment Securities

The amortized cost and fair value of investment securities are shown in the following tables. Management performs a quarterly evaluation of investment securities for any other-than-temporary impairment. For the three and nine month periods ended September 30, 2016 and 2015, there were no investment securities deemed to be other-than-temporarily impaired.

Investment securities at September 30, 2016, were as follows:



Securities Available-for-Sale (In thousands)	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Estimated Fair Value
Obligations of U.S. Treasury and other U.S. Government sponsored entities	$	270,000	$	—	$	855	$	269,145
U.S. Government sponsored entities' asset-backed securities	932,869		20,157		129		952,897
Other equity securities	1,119		1,688		—		2,807
Total	$	1,203,988	$	21,845	$	984	$	1,224,849



Securities Held-to-Maturity (In thousands)	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Estimated Fair Value
U.S. Government sponsored entities' asset-backed securities	$	81,812	$	1,885	$	19	$	83,678
Obligations of states and political subdivisions	113,283		3,777		$	200	116,860
Total	$	195,095	$	5,662	$	219	$	200,538

Securities with unrealized losses at September 30, 2016, were as follows:



	Unrealized loss position for less than 12 months				Unrealized loss position for 12 months or longer				Total
(In thousands)	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Securities Available-for-Sale
Obligations of U.S. Treasury and other U.S. Government sponsored entities	$	269,145	$	855	$	—	$	—	$	269,145	$	855
U.S. Government sponsored entities' asset-backed securities	48,885		64		$	28,993	65		$	77,878	129
Total	$	318,030	$	919	$	28,993	$	65	$	347,023	$	984
Securities Held-to-Maturity
U.S. Government sponsored entities' asset-backed securities	$	—	$	—	$	7,700	$	19	$	7,700	$	19
Obligations of states and political subdivisions	13,259		$	200	—		—		$	13,259	200
Total	$	13,259	$	200	$	7,700	$	19	$	20,959	$	219

Investment securities at December 31, 2015, were as follows:



Securities Available-for-Sale (In thousands)	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Estimated Fair Value
Obligations of U.S. Treasury and other U.S. Government sponsored entities	$	527,605	$	—	$	5,542	$	522,063
U.S. Government sponsored entities' asset-backed securities	907,989		8,776		5,272		911,493
Other equity securities	1,120		1,590		—		2,710
Total	$	1,436,714	$	10,366	$	10,814	$	1,436,266



Securities Held-to-Maturity (In thousands)	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Estimated Fair Value
Obligations of states and political subdivision	$	48,190	$	734	$	—	$	48,924
U.S. Government sponsored entities' asset-backed securities	101,112		1,526		134		102,504
Total	$	149,302	$	2,260	$	134	$	151,428

Securities with unrealized losses at December 31, 2015, were as follows:



	Unrealized loss position for less than 12 months				Unrealized loss position for 12 months or longer				Total
(In thousands)	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Securities Available-for-Sale
Obligations of U.S. Treasury and other U.S. Government sponsored entities	$	326,973	$	2,117	$	195,090	$	3,425	$	522,063	$	5,542
U.S. Government sponsored entities' asset-backed securities	384,169		2,776		114,543		2,496		498,712		5,272
Total	$	711,142	$	4,893	$	309,633	$	5,921	$	1,020,775	$	10,814
Securities Held-to-Maturity
U.S. Government sponsored entities' asset-backed securities	$	5,656	$	10	$	7,792	$	124	$	13,448	$	134

Management does not believe any of the unrealized losses at September 30, 2016 or December 31, 2015 represented other-than-temporary impairment. Should the impairment of any of these securities become other-than-temporary, the cost basis of the investment will be reduced and the resulting loss recognized within net income in the period the other-than-temporary impairment is identified.

Park’s U.S. Government sponsored entities' asset-backed securities consist of 15-year residential mortgage-backed securities and collateralized mortgage obligations.

The amortized cost and estimated fair value of investments in debt securities at September 30, 2016, are shown in the following table by contractual maturity, except for asset-backed securities, which are shown as a single total, due to the unpredictability of the timing of principal repayments.



Securities Available-for-Sale (In thousands)	Amortized cost		Fair value		Tax equivalent yield
Obligations of U.S. Treasury and other U.S. Government sponsored entities' obligations:
Due one through five years	$	270,000	269,145		1.18	%
Total	$	270,000	$	269,145	1.18	%


U.S. Government sponsored entities' asset-backed securities:	$	932,869	$	952,897	2.13	%



Securities Held-to-Maturity (In thousands)	Amortized cost		Fair value		Tax equivalent yield
Obligations of state and political subdivisions:
Due over ten years	$	113,283	$	116,860	4.35	%
Total	$	113,283	$	116,860	4.35	%

U.S. Government sponsored entities' asset-backed securities	$	81,812	$	83,678	3.31	%

All of Park’s securities shown in the table above as U.S. Treasury and other U.S. Government sponsored entities' notes are callable notes. These callable securities have final maturities of 1 to 4 years. Of the $269.1 million reported at September 30, 2016, none were expected to be called. The remaining average life of the investment portfolio is estimated to be 4.0 years.

There were no sales of investment securities during the three-month or nine-month periods ended September 30, 2016 or 2015.

Investment securities having an amortized cost of $1,033 million and $1,072 million at September 30, 2016 and December 31, 2015, respectively, were pledged to collateralize government and trust department deposits in accordance with federal and state requirements, to secure repurchase agreements sold and as collateral for FHLB advance borrowings.