2. Securities

The amortized cost and estimated fair value of securities classified as available for sale and held to maturity follow.



Securities Available for Sale
(in thousands)	September 30, 2016								December 31, 2015
			Gross		Gross						Gross		Gross
	Amortized		Unrealized		Unrealized		Fair		Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
US Treasury and government agency securities	$	20,604	$	67	$	—	$	20,671	$	135	$	—	$	1	$	134
Municipal obligations		214,403		3,024		409		217,018		39,410		235		38		39,607
Residential mortgage-backed securities		1,737,812		38,204		91		1,775,925		1,750,168		19,387		11,182		1,758,373
Commercial mortgage-backed securities		172,525		687		103		173,109		—		—		—		—
Collateralized mortgage obligations		220,912		2,344		—		223,256		291,085		140		2,192		289,033
Corporate debt securities		3,500		—		—		3,500		3,500		—		—		3,500
Equity securities		865		336		—		1,201		2,447		358		48		2,757
	$	2,370,621	$	44,662	$	603	$	2,414,680	$	2,086,745	$	20,120	$	13,461	$	2,093,404



Securities Held to Maturity
(in thousands)	September 30, 2016								December 31, 2015
			Gross		Gross						Gross		Gross
	Amortized		Unrealized		Unrealized		Fair		Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
US Treasury and government agency securities	$	50,000	$	860	$	—	$	50,860	$	50,000	$	—	$	410	$	49,590
Municipal obligations		541,839		11,182		1,462		551,559		185,890		3,475		1,166		188,199
Residential mortgage-backed securities		903,703		36,200		—		939,903		1,014,135		15,585		1,589		1,028,131
Collateralized mortgage obligations		932,890		8,767		1,439		940,218		1,120,363		2,244		12,676		1,109,931
	$	2,428,432	$	57,009	$	2,901	$	2,482,540	$	2,370,388	$	21,304	$	15,841	$	2,375,851

The following table presents the amortized cost and estimated fair value of debt securities at September 30, 2016 by contractual maturity. Actual maturities will differ from contractual maturities because of rights to call or repay obligations with or without penalties and scheduled and unscheduled principal payments on mortgage-backed securities and collateralized mortgage obligations.



(in thousands)	Amortized		Fair
Debt Securities Available for Sale	Cost		Value
Due in one year or less	$	4,864	$	4,900
Due after one year through five years		47,593		48,597
Due after five years through ten years		609,897		621,549
Due after ten years		1,707,402		1,738,433
Total available for sale debt securities	$	2,369,756	$	2,413,479

	Amortized		Fair
Debt Securities Held to Maturity	Cost		Value
Due in one year or less	$	14,982	$	15,019
Due after one year through five years		135,330		138,737
Due after five years through ten years		510,536		517,652
Due after ten years		1,767,584		1,811,132
Total held to maturity securities	$	2,428,432	$	2,482,540

The Company held no securities classified as trading at September 30, 2016 or December 31, 2015.

The details for securities classified as available for sale with unrealized losses for the periods indicated follow.



Available for Sale
September 30, 2016	Losses < 12 months				Losses 12 months or >				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(in thousands)	Value		Losses		Value		Losses		Value		Losses
Municipal obligations	$	69,801		409	$	—		—	$	69,801	$	409
Residential mortgage-backed securities		6,653		55		4,534		36		11,187		91
Commercial mortgage-backed securities		31,640		103		—		—		31,640		103
Collateralized mortgage obligations		6,910		—		—		—		6,910		—
	$	115,004	$	567	$	4,534	$	36	$	119,538	$	603



Available for Sale
December 31, 2015	Losses < 12 months				Losses 12 months or >				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(in thousands)	Value		Losses		Value		Losses		Value		Losses
US Treasury and government agency securities	$	—	$	—	$	82	$	1	$	82	$	1
Municipal obligations		8,296		38		—		—		8,296		38
Residential mortgage-backed securities		831,156		8,257		116,126		2,925		947,282		11,182
Collateralized mortgage obligations		208,397		1,257		33,138		935		241,535		2,192
Equity securities		20		1		1,473		47		1,493		48
	$	1,047,869	$	9,553	$	150,819	$	3,908	$	1,198,688	$	13,461

The details for securities classified as held to maturity with unrealized losses for the periods indicated follow.



Held to maturity
September 30, 2016	Losses < 12 months				Losses 12 months or >				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(in thousands)	Value		Losses		Value		Losses		Value		Losses
Municipal obligations	$	98,295	$	1,035	$	11,843	$	427	$	110,138	$	1,462
Collateralized mortgage obligations		119,172		146		132,960		1,293		252,132		1,439
	$	217,467	$	1,181	$	144,803	$	1,720	$	362,270	$	2,901



Held to maturity
December 31, 2015	Losses < 12 months				Losses 12 months or >				Total
			Gross				Gross				Gross
	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(in thousands)	Value		Losses		Value		Losses		Value		Losses
U.S. Treasury and government agency securities	$	45,590	$	410	$	—	$	—	$	45,590	$	410
Municipal obligations		22,652		301		48,727		865		71,379		1,166
Residential mortgage-backed securities		349,635		1,589		—		—		349,635		1,589
Collateralized mortgage obligations		516,330		2,894		370,756		9,782		887,086		12,676
	$	934,207	$	5,194	$	419,483	$	10,647	$	1,353,690	$	15,841

The unrealized losses primarily relate to changes in market rates on fixed-rate debt securities since the respective purchase dates. In all cases, the indicated impairment on these debt securities would be recovered no later than the security’s maturity date or possibly earlier if the market price for the security increases with a reduction in the yield required by the market. None of the unrealized losses relate to the marketability of the securities or the issuer’s ability to meet contractual obligations. The Company believes it has adequate liquidity and, therefore, does not plan to and, more likely than not, will not be required to sell these securities before recovery of the indicated impairment. Accordingly, the unrealized losses on these securities have been determined to be temporary.

Proceeds from the sales of securities were approximately $141.7 million with an associated realized gain of $1.5 million and $9.3 million with an associated gain of $0.3 million for the nine months ended September 30, 2016 and 2015, respectively.

Securities with carrying values totaling $3.7 billion at September 30, 2016 and $3.5 billion at December 31, 2015 were pledged as collateral primarily to secure public deposits or securities sold under agreements to repurchase.