Investment Securities Available for Sale and Investment Securities Held to Maturity

The following tables present the adjusted cost and approximate fair value of investment securities available for sale and investment securities held to maturity.



	March 31, 2017
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
	(In Thousands)
Investment securities available for sale:
Debt securities:
U.S. Treasury and other U.S. government agencies	$	2,995,084	$	4,896	$	32,595	$	2,967,385
Mortgage-backed securities	3,541,581		14,965		34,522		3,522,024
Collateralized mortgage obligations	5,013,180		5,796		84,833		4,934,143
States and political subdivisions	8,089		144		25		8,208
Other	14,129		48		116		14,061
Equity securities	400,727		70		—		400,797
Total	$	11,972,790	$	25,919	$	152,091	$	11,846,618
Investment securities held to maturity:
Collateralized mortgage obligations	$	77,791	$	4,926	$	3,424	$	79,293
Asset-backed securities	13,314		1,914		956		14,272
States and political subdivisions	1,002,928		3,302		20,680		985,550
Other	64,752		928		2,101		63,579
Total	$	1,158,785	$	11,070	$	27,161	$	1,142,694



	December 31, 2016
			Gross Unrealized
	Amortized Cost		Gains		Losses		Fair Value
	(In Thousands)
Investment securities available for sale:
Debt securities:
U.S. Treasury and other U.S. government agencies	$	2,409,141	$	2,390	$	37,200	$	2,374,331
Mortgage-backed securities	3,796,270		12,869		45,801		3,763,338
Collateralized mortgage obligations	5,200,241		5,292		106,605		5,098,928
States and political subdivisions	8,457		184		—		8,641
Other	16,321		6		142		16,185
Equity securities	403,548		84		—		403,632
Total	$	11,833,978	$	20,825	$	189,748	$	11,665,055
Investment securities held to maturity:
Collateralized mortgage obligations	$	83,087	$	5,265	$	3,278	$	85,074
Asset-backed securities	15,118		1,982		1,081		16,019
States and political subdivisions	1,040,716		2,309		25,518		1,017,507
Other	64,296		1,143		2,030		63,409
Total	$	1,203,217	$	10,699	$	31,907	$	1,182,009

In the above tables, equity securities include $400 million and $403 million at March 31, 2017 and December 31, 2016, respectively, of FHLB and Federal Reserve stock carried at par.

The investments held within the states and political subdivision caption of investment securities held to maturity relate to private placement transactions underwritten as loans by the Company but that meet the definition of a security within ASC Topic 320, Investments – Debt and Equity Securities.

The following tables disclose the fair value and the gross unrealized losses of the Company’s available for sale securities and held to maturity securities that were in a loss position at March 31, 2017 and December 31, 2016. This information is aggregated by investment category and the length of time the individual securities have been in an unrealized loss position.



	March 31, 2017
	Securities in a loss position for less than 12 months				Securities in a loss position for 12 months or longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(In Thousands)
Investment securities available for sale:
Debt securities:
U.S. Treasury and other U.S. government agencies	$	1,342,663	$	13,129	$	747,898	$	19,466	$	2,090,561	$	32,595
Mortgage-backed securities	1,202,675		9,804		1,293,140		24,718		2,495,815		34,522
Collateralized mortgage obligations	2,979,987		68,468		1,074,947		16,365		4,054,934		84,833
States and political subdivisions	4,333		25		—		—		4,333		25
Other	3,871		55		1,060		61		4,931		116
Total	$	5,533,529	$	91,481	$	3,117,045	$	60,610	$	8,650,574	$	152,091

Investment securities held to maturity:
Collateralized mortgage obligations	$	8,468	$	199	$	40,759	$	3,225	$	49,227	$	3,424
Asset-backed securities	—		—		8,317		956		8,317		956
States and political subdivisions	422,213		9,863		311,319		10,817		733,532		20,680
Other	9,380		130		10,872		1,971		20,252		2,101
Total	$	440,061	$	10,192	$	371,267	$	16,969	$	811,328	$	27,161



	December 31, 2016
	Securities in a loss position for less than 12 months				Securities in a loss position for 12 months or longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
	(In Thousands)
Investment securities available for sale:
Debt securities:
U.S. Treasury and other U.S. government agencies	$	1,277,341	$	23,862	$	609,078	$	13,338	$	1,886,419	$	37,200
Mortgage-backed securities	1,425,743		15,235		1,368,957		30,566		2,794,700		45,801
Collateralized mortgage obligations	3,527,757		99,477		782,849		7,128		4,310,606		106,605
Other	3,849		77		1,057		65		4,906		142
Total	$	6,234,690	$	138,651	$	2,761,941	$	51,097	$	8,996,631	$	189,748

Investment securities held to maturity:
Collateralized mortgage obligations	$	3,847	$	527	$	40,083	$	2,751	$	43,930	$	3,278
Asset-backed securities	343		1		9,238		1,080		9,581		1,081
States and political subdivisions	532,090		13,043		313,803		12,475		845,893		25,518
Other	16,578		174		3,587		1,856		20,165		2,030
Total	$	552,858	$	13,745	$	366,711	$	18,162	$	919,569	$	31,907

As indicated in the previous tables, at March 31, 2017, the Company held certain investment securities in unrealized loss positions. The Company does not have the intent to sell these securities and believes it is not more likely than not that it will be required to sell these securities before their anticipated recovery.

The Company regularly evaluates each available for sale and held to maturity security in a loss position for OTTI. In its evaluation, the Company considers such factors as the length of time and the extent to which the fair value has been below cost, the financial condition of the issuer, the Company’s intent to hold the security to an expected recovery in market value and whether it is more likely than not that the Company will have to sell the security before its fair value recovers. Activity related to the credit loss component of the OTTI is recognized in earnings. The portion of OTTI related to all other factors is recognized in other comprehensive income.

Management does not believe that any individual unrealized loss in the Company’s investment securities available for sale or held to maturity portfolios, presented in the preceding tables, represents an OTTI at either March 31, 2017 or December 31, 2016, other than those noted below.

The following table discloses activity related to credit losses for debt securities where a portion of the OTTI was recognized in other comprehensive income.



	Three Months Ended March 31,
	2017		2016
	(In Thousands)
Balance at beginning of period	$	22,582	$	22,452
Reductions for securities paid off during the period (realized)	—		—
Additions for the credit component on debt securities in which OTTI was not previously recognized	242		—
Additions for the credit component on debt securities in which OTTI was previously recognized	—		—
Balance at end of period	$	22,824	$	22,452

For the three months ended March 31, 2017, there was $242 thousand of OTTI recognized on held to maturity securities. For the three months ended March 31, 2016, there was no OTTI recognized on held to maturity securities. The investment securities primarily impacted by credit impairment are held to maturity non-agency collateralized mortgage obligations.

The contractual maturities of the securities portfolios are presented in the following table.



March 31, 2017	Amortized Cost		Fair Value
	(In Thousands)
Investment securities available for sale:
Maturing within one year	$	350,956	$	350,702
Maturing after one but within five years	621,527		612,890
Maturing after five but within ten years	1,027,104		1,027,567
Maturing after ten years	1,017,715		998,495
	3,017,302		2,989,654
Mortgage-backed securities and collateralized mortgage obligations	8,554,761		8,456,167
Equity securities	400,727		400,797
Total	$	11,972,790	$	11,846,618

Investment securities held to maturity:
Maturing within one year	$	67,232	$	67,298
Maturing after one but within five years	274,836		269,078
Maturing after five but within ten years	233,024		229,624
Maturing after ten years	505,902		497,401
	1,080,994		1,063,401
Collateralized mortgage obligations	77,791		79,293
Total	$	1,158,785	$	1,142,694

The gross realized gains and losses recognized on sales of investment securities available for sale are shown in the table below.



	Three Months Ended March 31,
	2017		2016
	(In Thousands)
Gross gains	$	—	$	8,353
Gross losses	—		—
Net realized gains	$	—	$	8,353