Investment Securities

The following tables are a summary of the available-for-sale and held-to-maturity securities portfolios as of the dates shown:



	June 30, 2017
(Dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available-for-sale securities
U.S. Treasury	$	119,804	$	—	$	(723	)	$	119,081
U.S. Government agencies	158,162		22		(674		)	157,510
Municipal	121,610		2,774		(264		)	124,120
Corporate notes:
Financial issuers	60,340		71		(810		)	59,601
Other	1,000		—		(3		)	997
Mortgage-backed: ⁽¹⁾
Mortgage-backed securities	1,139,734		2,301		(31,704		)	1,110,331
Collateralized mortgage obligations	42,845		433		(319		)	42,959
Equity securities	32,642		3,028		(633		)	35,037
Total available-for-sale securities	$	1,676,137	$	8,629	$	(35,130	)	$	1,649,636
Held-to-maturity securities
U.S. Government agencies	$	585,071	$	556	$	(7,461	)	$	578,166
Municipal	208,305		2,298		(1,280		)	209,323
Total held-to-maturity securities	$	793,376	$	2,854	$	(8,741	)	$	787,489



	December 31, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
(Dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available-for-sale securities
U.S. Treasury	$	142,741	$	1	$	(759	)	$	141,983
U.S. Government agencies	189,540		47		(435		)	189,152
Municipal	129,446		2,969		(606		)	131,809
Corporate notes:
Financial issuers	65,260		132		(1,000		)	64,392
Other	1,000		—		(1		)	999
Mortgage-backed: ⁽¹⁾
Mortgage-backed securities	1,185,448		284		(54,330		)	1,131,402
Collateralized mortgage obligations	30,105		67		(490		)	29,682
Equity securities	32,608		3,429		(789		)	35,248
Total available-for-sale securities	$	1,776,148	$	6,929	$	(58,410	)	$	1,724,667
Held-to-maturity securities
U.S. Government agencies	$	433,343	$	7	$	(24,470	)	$	408,880
Municipal	202,362		647		(4,287		)	198,722
Total held-to-maturity securities	$	635,705	$	654	$	(28,757	)	$	607,602



	June 30, 2016
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
(Dollars in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available-for-sale securities
U.S. Treasury	$	122,296	$	35	$	(1	)	$	122,330
U.S. Government agencies	69,678		238		—			69,916
Municipal	108,179		3,588		(127		)	111,640
Corporate notes:
Financial issuers	68,097		1,502		(1,411		)	68,188
Other	1,500		2		—			1,502
Mortgage-backed: ⁽¹⁾
Mortgage-backed securities	162,593		4,280		(150		)	166,723
Collateralized mortgage obligations	40,419		457		(91		)	40,785
Equity securities	51,426		5,544		(391		)	56,579
Total available-for-sale securities	$	624,188	$	15,646	$	(2,171	)	$	637,663
Held-to-maturity securities
U.S. Government agencies	$	789,482	$	11,861	$	(647	)	$	800,696
Municipal	202,729		6,967		(213		)	209,483
Total held-to-maturity securities	$	992,211	$	18,828	$	(860	)	$	1,010,179


(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 and held-to-maturity securities portfolios which has gross unrealized losses, reflecting the length of time that individual securities have been in a continuous unrealized loss position at June 30, 2017:



	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
Available-for-sale securities
U.S. Treasury	$	119,081	$	(723	)	$	—	$	—		$	119,081	$	(723	)
U.S. Government agencies	152,149		(674		)	—		—			152,149		(674		)
Municipal	145,960		(155		)	5,852		(109		)	151,812		(264		)
Corporate notes:
Financial issuers	—		—			35,154		(810		)	35,154		(810		)
Other	997		(3		)	—		—			997		(3		)
Mortgage-backed:
Mortgage-backed securities	932,800		(31,704		)	—		—			932,800		(31,704		)
Collateralized mortgage obligations	11,809		(122		)	7,353		(197		)	19,162		(319		)
Equity securities	10,189		(271		)	5,138		(362		)	15,327		(633		)
Total available-for-sale securities	$	1,372,985	$	(33,652	)	$	53,497	$	(1,478	)	$	1,426,482	$	(35,130	)
Held-to-maturity securities
U.S. Government agencies	$	363,692	$	(7,461	)	$	—	$	—		$	363,692	$	(7,461	)
Municipal	73,447		(1,280		)	—		—			73,447		(1,280		)
Total held-to-maturity securities	$	437,139	$	(8,741	)	$	—	$	—		$	437,139	$	(8,741	)

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 June 30, 2017 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 corporate notes and mortgage-backed securities. Unrealized losses recognized on corporate notes and mortgage-backed securities are the result of increases in yields for similar types of securities.

The following table provides information as to the amount of gross gains and gross losses realized and proceeds received through the sale or call of investment securities:



	Three months ended June 30,						Six months ended June 30,
(Dollars in thousands)	2017			2016			2017			2016
Realized gains	$	48		$	1,487		$	48		$	4,037
Realized losses	(1		)	(47		)	(56		)	(1,272		)
Net realized gains (losses)	$	47		$	1,440		$	(8	)	$	2,765
Other than temporary impairment charges	—			—			—			—
Gains (losses) on investment securities, net	$	47		$	1,440		$	(8	)	$	2,765
Proceeds from sales and calls of available-for-sale securities	$	3,724		$	1,068,795		$	9,729		$	1,071,996
Proceeds from calls of held-to-maturity securities	2			183,738			51,062			281,981

The amortized cost and fair value of securities as of June 30, 2017, December 31, 2016 and June 30, 2016, 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 determined to be available-for-sale 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:



	June 30, 2017				December 31, 2016				June 30, 2016
(Dollars in thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value		Amortized Cost		Fair Value
Available-for-sale securities
Due in one year or less	$	125,706	$	125,170	$	145,353	$	145,062	$	214,917	$	215,290
Due in one to five years	289,688		289,243		321,019		320,423		113,263		113,395
Due in five to ten years	38,213		39,463		27,319		28,451		28,111		30,870
Due after ten years	7,309		7,433		34,296		34,399		13,459		14,021
Mortgage-backed	1,182,579		1,153,290		1,215,553		1,161,084		203,012		207,508
Equity securities	32,642		35,037		32,608		35,248		51,426		56,579
Total available-for-sale securities	$	1,676,137	$	1,649,636	$	1,776,148	$	1,724,667	$	624,188	$	637,663
Held-to-maturity securities
Due in one year or less	$	—	$	—	$	—	$	—	$	—	$	—
Due in one to five years	32,925		32,776		29,794		29,416		27,505		27,738
Due in five to ten years	172,398		172,800		69,664		67,820		68,691		70,121
Due after ten years	588,053		581,913		536,247		510,366		896,015		912,320
Total held-to-maturity securities	$	793,376	$	787,489	$	635,705	$	607,602	$	992,211	$	1,010,179

Securities having a fair value of $1.5 billion at June 30, 2017 as well as securities having a fair value of $1.4 billion at December 31, 2016 and June 30, 2016 were pledged as collateral for public deposits, trust deposits, Federal Home Loan Bank ("FHLB") advances, securities sold under repurchase agreements and derivatives. At June 30, 2017, there were no securities of a single issuer, other than U.S. Government-sponsored agency securities, which exceeded 10% of shareholders’ equity.