Available-for-Sale Securities

A summary of the available-for-sale securities portfolio presenting carrying amounts and gross unrealized gains and losses as of December 31, 2014 and 2013 is as follows:



	December 31, 2014									December 31, 2013
(Dollars in thousands)	Amortized Cost		Gross unrealized gains		Gross unrealized losses			Fair Value		Amortized Cost		Gross unrealized gains		Gross unrealized losses			Fair Value
U.S. Treasury	$	388,713	$	84	$	(6,992	)	$	381,805	$	354,262	$	141	$	(18,308	)	$	336,095
U.S. Government agencies	686,106		4,113		(21,903		)	668,316		950,086		1,680		(56,078		)	895,688
Municipal	234,951		5,318		(1,740		)	238,529		154,463		2,551		(4,298		)	152,716
Corporate notes:
Financial issuers	129,309		2,006		(1,557		)	129,758		129,362		1,993		(2,411		)	128,944
Other	3,766		55		—			3,821		5,994		105		(5		)	6,094
Mortgage-backed: ⁽¹⁾
Mortgage-backed securities	271,129		5,448		(4,928		)	271,649		562,708		3,537		(18,047		)	548,198
Collateralized mortgage obligations	47,347		249		(535		)	47,061		57,711		258		(942		)	57,027
Equity securities	46,592		4,872		(325		)	51,139		50,532		1,493		(497		)	51,528
Total available-for-sale securities	$	1,807,913	$	22,145	$	(37,980	)	$	1,792,078	$	2,265,118	$	11,758	$	(100,586	)	$	2,176,290


(1)	Consisting entirely of residential mortgage-backed securities, none of which are subprime.

The following table presents the portion of the Company’s available-for-sale securities portfolio which has gross unrealized losses, reflecting the length of time that individual securities have been in a continuous unrealized loss position at December 31, 2014:



	Continuous unrealized losses existing for less than 12 months					Continuous unrealized losses existing for greater than 12 months					Total
(Dollars in thousands)	Fair value		Unrealized losses			Fair value		Unrealized losses			Fair value		Unrealized losses
U.S. Treasury	$	97,395	$	(31	)	$	193,187	$	(6,961	)	$	290,582	$	(6,992	)
U.S. Government agencies	13,164		(120		)	459,035		(21,783		)	472,199		(21,903		)
Municipal	40,904		(315		)	45,438		(1,425		)	86,342		(1,740		)
Corporate notes:
Financial issuers	1,311		(1		)	57,624		(1,556		)	58,935		(1,557		)
Other	—		—			—		—			—		—
Mortgage-backed:
Mortgage-backed securities	4,875		(60		)	142,301		(4,868		)	147,176		(4,928		)
Collateralized mortgage obligations	13,198		(13		)	14,828		(522		)	28,026		(535		)
Equity securities	—		—			9,462		(325		)	9,462		(325		)
Total	$	170,847	$	(540	)	$	921,875	$	(37,440	)	$	1,092,722	$	(37,980	)



	Continuous unrealized losses existing for less than 12 months					Continuous unrealized losses existing for greater than 12 months					Total
(Dollars in thousands)	Fair value		Unrealized losses			Fair value		Unrealized losses			Fair value		Unrealized losses
U.S. Treasury	$	75,695	$	(62	)	$	181,922	$	(18,246	)	$	257,617	$	(18,308	)
U.S. Government agencies	399,982		(47,860		)	53,431		(8,218		)	453,413		(56,078		)
Municipal	66,368		(3,757		)	10,529		(541		)	76,897		(4,298		)
Corporate notes:
Financial issuers	21,296		(49		)	66,834		(2,362		)	88,130		(2,411		)
Other	995		(5		)	—		—			995		(5		)
Mortgage-backed:
Mortgage-backed securities	270,522		(18,008		)	2,922		(39		)	273,444		(18,047		)
Collateralized mortgage obligations	40,449		(942		)	—		—			40,449		(942		)
Equity securities	8,272		(205		)	5,709		(292		)	13,981		(497		)
Total	$	883,579	$	(70,888	)	$	321,347	$	(29,698	)	$	1,204,926	$	(100,586	)

The Company conducts a regular assessment of its investment securities to determine whether securities are other-than-temporarily impaired considering, among other factors, the nature of the securities, credit ratings or financial condition of the issuer, the extent and duration of the unrealized loss, expected cash flows, market conditions and the Company’s ability to hold the securities through the anticipated recovery period.

The Company does not consider securities with unrealized losses at December 31, 2014 to be other-than-temporarily impaired. The Company does not intend to sell these investments and it is more likely than not that the Company will not be required to sell these investments before recovery of the amortized cost bases, which may be the maturity dates of the securities. The unrealized losses within each category have occurred as a result of changes in interest rates, market spreads and market conditions subsequent to purchase. Securities with continuous unrealized losses existing for more than twelve months were primarily agency bonds, treasury notes and mortgage-backed securities. Unrealized losses recognized on agency bonds, treasury notes and mortgage-backed securities are the result of increases in yields for similar types of securities which have a longer duration and maturity.

In 2013, the Company recorded an other-than-temporary impairment charge related to a money market preferred security. The Company recognized this charge because it estimated that it would not be able to recover its amortized basis prior to its anticipated sale of the security as a result of the Volcker Rule.

The following table provides information as to the amount of gross gains and gross losses realized and proceeds received through the sales of available-for-sale investment securities:



	Years Ended December 31,
(Dollars in thousands)	2014			2013			2012
Realized gains	$	405		$	434		$	4,918
Realized losses	(909		)	(106		)	(23		)
Net realized gains	$	(504	)	$	328		$	4,895
Other than temporary impairment charges	—			(3,328		)	—
(Losses) gains on available-for-sale securities, net	$	(504	)	$	(3,000	)	$	4,895
Proceeds from sales of available-for-sale securities, net	$	852,330		$	138,274		$	2,399,035

Net losses on available-for-sale securities resulted in an income tax benefit included in total income tax expense of $194,000 and $1.2 million in 2014 and 2013, respectively. Net gains on available-for-sale securities resulted in income tax expense of $1.9 million in 2012.

The amortized cost and fair value of securities as of December 31, 2014 and December 31, 2013, by contractual maturity, are shown in the following table. Contractual maturities may differ from actual maturities as borrowers may have the right to call or repay obligations with or without call or prepayment penalties. Mortgage-backed securities are not included in the maturity categories in the following maturity summary as actual maturities may differ from contractual maturities because the underlying mortgages may be called or prepaid without penalties:



	December 31, 2014				December 31, 2013
(Dollars in thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	285,596	$	285,889	$	268,847	$	269,168
Due in one to five years	172,647		172,885		358,108		358,357
Due in five to ten years	331,389		325,644		350,372		330,020
Due after ten years	653,213		637,811		616,840		561,992
Mortgage-backed	318,476		318,710		620,419		605,225
Equity securities	46,592		51,139		50,532		51,528
Total available-for-sale securities	$	1,807,913	$	1,792,078	$	2,265,118	$	2,176,290

At December 31, 2014 and December 31, 2013, securities having a carrying value of $1.1 billion and $1.2 billion, respectively, were pledged as collateral for public deposits, trust deposits, FHLB advances, securities sold under repurchase agreements and derivatives. At December 31, 2014, there were no securities of a single issuer, other than U.S. Government-sponsored agency securities, which exceeded 10% of shareholders’ equity.