Note 2. Securities

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



Securities Available for Sale
	December 31, 2016								December 31, 2015
			Gross		Gross						Gross		Gross
	Amortized		Unrealized		Unrealized		Fair		Amortized		Unrealized		Unrealized		Fair
(in thousands)	Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
U.S. Treasury and government agency securities	$	56,751	$	—	$	1,923	$	54,828	$	135	$	—	$	1	$	134
Municipal obligations		253,228		113		11,186		242,155		39,410		235		38		39,607
Residential mortgage-backed securities		1,620,191		10,592		19,428		1,611,355		1,750,168		19,387		11,182		1,758,373
Commercial mortgage-backed securities		425,750		—		23,159		402,591		—		—		—		—
Collateralized mortgage obligations		202,580		490		591		202,479		291,085		140		2,192		289,033
Corporate debt securities		3,500		—		—		3,500		3,500		—		—		3,500
Equity securities		—		—		—		—		2,447		358		48		2,757
	$	2,562,000	$	11,195	$	56,287	$	2,516,908	$	2,086,745	$	20,120	$	13,461	$	2,093,404



Securities Held to Maturity
	December 31, 2016								December 31, 2015
			Gross		Gross						Gross		Gross
	Amortized		Unrealized		Unrealized		Fair		Amortized		Unrealized		Unrealized		Fair
(in thousands)	Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
U.S. Treasury and government agency securities	$	50,000	$	—	$	44	$	49,956	$	50,000	$	—	$	410	$	49,590
Municipal obligations		648,093		2,147		20,175		630,065		185,890		3,475		1,166		188,199
Residential mortgage-backed securities		862,162		4,329		3,068		863,423		1,014,135		15,585		1,589		1,028,131
Commercial mortgage-backed securities		75,739		—		4,038		71,701		—		—		—		—
Collateralized mortgage obligations		864,226		1,420		10,674		854,972		1,120,363		2,244		12,676		1,109,931
	$	2,500,220	$	7,896	$	37,999	$	2,470,117	$	2,370,388	$	21,304	$	15,841	$	2,375,851

The following tables present the amortized cost and fair value of debt securities at December 31, 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 collateral mortgage obligations.



(in thousands)	Amortized Cost		Fair Value
Debt Securities Available for Sale
Due in one year or less	$	4,523	$	4,536
Due after one year through five years		42,881		43,424
Due after five years through ten years		992,327		964,119
Due after ten years		1,522,269		1,504,829
Total available for sale debt securities	$	2,562,000	$	2,516,908



(in thousands)	Amortized Cost		Fair Value
Debt Securities Held to Maturity
Due in one year or less	$	6,727	$	6,740
Due after one year through five years		135,187		136,268
Due after five years through ten years		691,248		668,507
Due after ten years		1,667,058		1,658,602
Total held to maturity debt securities	$	2,500,220	$	2,470,117

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

The details for securities classified as available for sale with unrealized losses as of December 31, 2016 follow:



Available for sale
	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	$	54,788	$	1,923	$	—	$	—	$	54,788	$	1,923
Municipal obligations		228,588		11,186		—		—		228,588		11,186
Residential mortgage-backed securities		1,087,644		19,359		3,738		69		1,091,382		19,428
Commercial mortgage-backed securities		402,591		23,159		—		—		402,591		23,159
Collateralized mortgage obligations		83,701		591		—		—		83,701		591
	$	1,857,312	$	56,218	$	3,738	$	69	$	1,861,050	$	56,287

The details for securities classified as available for sale with unrealized losses as of December 31, 2015 follow:



Available for sale
	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	$	—	$	—	$	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 as of December 31, 2016 follow:



Held to maturity
	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	$	49,956	$	44	$	—	$	—	$	49,956	$	44
Municipal obligations		494,470		19,706		11,750		469		506,220		20,175
Residential mortgage-backed securities		278,369		3,068		—		—		278,369		3,068
Commercial mortgage-backed securities		71,701		4,038		—		—		71,701		4,038
Collateralized mortgage obligations		618,739		7,296		115,375		3,378		734,114		10,674
	$	1,513,235	$	34,152	$	127,125	$	3,847	$	1,640,360	$	37,999

The details for securities classified as held to maturity with unrealized losses as of December 31, 2015 follow:



Held to maturity
	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 date. 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 sales of securities were approximately $173.2 million in 2016, $9.3 million in 2015, and $1.5 million in 2014. Gross gains of approximately $2.0 million and gross losses of approximately $0.2 million were recognized on sales of securities in 2016. Gross gains and losses recognized on sales of securities in 2015 were insignificant.

Securities with carrying values totaling approximately $3.8 billion at December 31, 2016 and $3.5 billion at December 31, 2015 were pledged primarily to secure public deposits or sold under agreements to repurchase.