Investment Securities

Trading securities totaled $3.4 million and $3.0 million at March 31, 2016 and December 31, 2015, respectively.

The amortized cost and estimated fair value of investment securities available-for-sale and held-to-maturity at March 31, 2016 and December 31, 2015, are presented below:



(Dollars in thousands)	March 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Available-for-Sale
Corporate bonds	$	42,959	$	23	$	3,170	$	39,812
Mortgage-backed securities—residential issued by government sponsored entities	611,433		9,603		172		620,864
Industrial revenue bonds	3,239		10		—		3,249
Total	$	657,631	$	9,636	$	3,342	$	663,925
Held-to-Maturity
U.S. Government agencies	$	12,491	$	456	$	—	$	12,947
Corporate bonds	74,016		232		3,000		71,248
State and political subdivisions—tax exempt	10,533		601		—		11,134
State and political subdivisions—taxable	526		24		—		550
Mortgage-backed securities—residential issued by government sponsored entities	362,917		8,593		17		371,493
Total	$	460,483	$	9,906	$	3,017	$	467,372



(Dollars in thousands)	December 31, 2015
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Available-for-Sale
Corporate bonds	$	22,870	$	112	$	227	$	22,755
Mortgage-backed securities—residential issued by government sponsored entities	614,176		1,376		4,415		611,137
Industrial revenue bonds	3,409		28		—		3,437
Total	$	640,455	$	1,516	$	4,642	$	637,329
Held-to-Maturity
U.S. Government agencies	$	12,805	$	230	$	—	$	13,035
Corporate bonds	70,059		—		401		69,658
State and political subdivisions—tax exempt	10,849		488		—		11,337
State and political subdivisions—taxable	528		17		—		545
Mortgage-backed securities—residential issued by government sponsored entities	378,264		3,107		812		380,559
Total	$	472,505	$	3,842	$	1,213	$	475,134

There were no sales of securities during the three months ended March 31, 2016. Proceeds from sales of securities and gross gains realized on sales of investments during for the three months ended March 31, 2015 were $20.3 million and $0.1 million respectively.

The estimated fair value of investment securities at March 31, 2016, by contractual maturity, is shown in the table that follows. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations without call or prepayment penalties. Debt securities not due at a single maturity date are shown separately.



(Dollars in thousands)	March 31, 2016
	Amortized Cost		Estimated Fair Value		Yield
Available-for-sale
Due in one year or less	$	—	$	—	—	%
Due after one year through five years	—		—		—	%
Due after five years through ten years	—		—		—	%
Due after ten years	46,198		43,061		2.95	%
Mortgage-backed securities—residential issued by government sponsored entities	611,433		620,864		2.09	%
Total	$	657,631	$	663,925	2.14	%

	Amortized Cost		Estimated Fair Value		Yield
Held-to-maturity
Due in one year or less	$	—	$	—	—	%
Due after one year through five years	19,311		18,330		4.37	%
Due after five years through ten years	65,238		64,052		4.89	%
Due after ten years	13,017		13,497		2.87	%
Mortgage-backed securities—residential issued by government sponsored entities	362,917		371,493		2.40	%
Total	$	460,483	$	467,372	2.83	%

Securities with unrealized losses not recognized in income, and the period of time they have been in an unrealized loss position, are as follows:



(Dollars in thousands)	Less than 12 Months				12 Months or Longer				Total
March 31, 2016	Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
Available-for-Sale
Corporate bonds	$	35,791	$	3,170	$	—	$	—	$	35,791	$	3,170
Mortgage-backed securities—residential issued by government sponsored entities	43,975		76		30,090		96		74,065		172
Total	$	79,766	$	3,246	$	30,090	$	96	$	109,856	$	3,342
Held-to-Maturity
U.S. government agencies	$	—	$	—	$	12,947	$	100	$	12,947	$	100
Corporate bonds	41,391		2,571		4,625		429		46,016		3,000
Mortgage-backed securities—residential issued by government sponsored entities	27,033		128		122,880		546		149,913		674
Total	$	68,424	$	2,699	$	140,452	$	1,075	$	208,876	$	3,774



(Dollars in thousands)	Less than 12 Months				12 Months or Longer				Total
December 31, 2015	Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
Available-for-Sale
Corporate bonds	$	8,237	$	227	$	—	$	—	$	8,237	$	227
Mortgage-backed securities—residential issued by government sponsored entities	378,852		3,723		31,273		692		410,125		4,415
Total	$	387,089	$	3,950	$	31,273	$	692	$	418,362	$	4,642
Held-to-Maturity
Corporate bonds	$	—	$	—	$	13,035	$	351	$	13,035	$	351
U.S Government agencies	44,658		401		—		—		44,658		401
Mortgage-backed securities—residential issued by government sponsored entities	143,368		1,691		143,147		3,298		286,515		4,989
Total	$	188,026	$	2,092	$	156,182	$	3,649	$	344,208	$	5,741

As of March 31, 2016, the Company’s security portfolio consisted of 135 securities, 15 of which were in an unrealized loss position. The majority of unrealized losses are related to the Company’s corporate securities and mortgage-backed securities.

The corporate bonds in an unrealized loss position at March 31, 2016 and December 31, 2015 continue to perform and are expected to perform through maturity. Unrealized losses associated with these securities are primarily due to changes in interest rates and market volatility, and the corporate issuers have not experienced significant adverse events that would call into question their ability to repay those debt obligations according to contractual terms. Further, because the Company does not have the intent to sell these corporate bonds and it is more likely than not that it will not be required to sell the securities before their anticipated recovery of their amortized cost bases, the Company does not consider these securities to be other-than-temporarily-impaired as of March 31, 2016 or December 31, 2015.

All of the mortgage-backed securities at March 31, 2016 and December 31, 2015 were issued by U.S. government-sponsored entities and agencies, which the government has affirmed its commitment to support. Unrealized losses associated with these securities are attributable to changes in interest rates and illiquidity, and not credit quality, and because the Company does not have the intent to sell these mortgage-backed securities and it is more likely than not that it will not be required to sell the securities before their anticipated recovery, the Company does not consider these securities to be other-than-temporarily impaired at March 31, 2016 or December 31, 2015.

Investment securities having carrying values of approximately $362.4 million and $311.5 million at March 31, 2016 and December 31, 2015, respectively, were pledged to secure public funds on deposit, securities sold under agreements to repurchase, and for other purposes as required by law.