Investment Securities

3 Months Ended

Mar. 31, 2019

Investments, Debt and Equity Securities [Abstract]

The following table presents the amortized cost and estimated fair values of investment securities:



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
March 31, 2019	(in thousands)
Available for Sale
U.S. Government sponsored agency securities	$	26,900	$	624	$	—		$	27,524
State and municipal securities	293,116		5,840		(1,272		)	297,684
Corporate debt securities	122,006		1,610		(2,328		)	121,288
Collateralized mortgage obligations	889,046		5,561		(7,202		)	887,405
Residential mortgage-backed securities	447,924		1,530		(8,596		)	440,858
Commercial mortgage-backed securities	282,483		1,320		(1,566		)	282,237
Auction rate securities	107,410		—		(4,600		)	102,810
Total	$	2,168,885	$	16,485	$	(25,564	)	$	2,159,806

Held to Maturity
State and municipal securities	$	155,998	$	5,710	$	—		$	161,708
Residential mortgage-backed securities	432,445		9,454		—			441,899
Total	$	588,443	$	15,164	$	—		$	603,607



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
December 31, 2018	(in thousands)
Available for Sale
U.S. Government sponsored agency securities	$	31,586	$	185	$	(139	)	$	31,632
State and municipal securities	282,383		2,178		(5,466		)	279,095
Corporate debt securities	111,454		1,432		(3,353		)	109,533
Collateralized mortgage obligations	841,294		2,758		(11,972		)	832,080
Residential mortgage-backed securities	476,973		1,583		(15,212		)	463,344
Commercial mortgage-backed securities	264,165		524		(3,073		)	261,616
Auction rate securities	107,410		—		(4,416		)	102,994
Total	$	2,115,265	$	8,660	$	(43,631	)	$	2,080,294

Held to Maturity
State and municipal securities	$	156,134	$	1,166	$	(93	)	$	157,207
Residential mortgage-backed securities	450,545		3,667		—			454,212
Total	$	606,679	$	4,833	$	(93	)	$	611,419

Securities carried at $896.6 million at March 31, 2019 and $973.4 million at December 31, 2018, were pledged as collateral to secure public and trust deposits and customer repurchase agreements.

The amortized cost and estimated fair values of debt securities as of March 31, 2019, by contractual maturity, are shown in the following table. Actual maturities may differ from contractual maturities as certain investment securities are subject to call or prepayment with or without call or prepayment penalties.



		Available for Sale				Held to Maturity
		Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
	(in thousands)
Due in one year or less		$	9,252	$	9,256	$	—	$	—
Due from one year to five years		55,635		57,030		—		—
Due from five years to ten years		120,920		120,605		—		—
Due after ten years		363,625		362,415		155,998		161,708
		549,432		549,306		155,998		161,708
Residential mortgage-backed securities⁽¹⁾		447,924		440,858		432,445		441,899
Commercial mortgage-backed securities⁽¹⁾		282,483		282,237		—		—
Collateralized mortgage obligations⁽¹⁾		889,046		887,405		—		—
Total		$	2,168,885	$	2,159,806	$	588,443	$	603,607

(1) Maturities for mortgage-backed securities and collateralized mortgage obligations are dependent upon the interest rate environment and prepayments on the underlying loans.

The following table presents information related to the gross realized gains and losses on the sales of equity and debt securities:



	Gross Realized Gains		Gross Realized Losses			Net Gains
Three months ended March 31, 2019	(in thousands)
Debt securities	257		(192		)	65
Total	$	257	$	(192	)	$	65
Three months ended March 31, 2018
Equity securities	$	9	$	—		$	9
Debt securities	10		—			10
Total	$	19	$	—		$	19

The cumulative balance of credit-related other-than-temporary impairment charges, previously recognized as components of earnings, for debt securities held by the Corporation at March 31, 2019 and March 31, 2018 was $11.5 million. There were no other-than-temporary impairment charges recognized for the three months ended March 31, 2019 or March 31, 2018.

The following table presents the gross unrealized losses and estimated fair values of investments, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at March 31, 2019 and December 31, 2018:



	Less than 12 months						12 months or longer						Total
March 31, 2019	Number of Securities	Estimated Fair Value		Unrealized Losses			Number of Securities	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
Available for Sale		(in thousands)
State and municipal securities	—	$	—	$	—		39	$	84,753	$	(1,272	)	$	84,753	$	(1,272	)
Corporate debt securities	8	26,514		(190		)	14	26,646		(2,138		)	53,160		(2,328		)
Collateralized mortgage obligations	6	707		(1		)	90	418,166		(7,201		)	418,873		(7,202		)
Residential mortgage-backed securities	—	—		—			116	403,327		(8,596		)	403,327		(8,596		)
Commercial mortgage-backed securities	—	—		—			23	182,150		(1,566		)	182,150		(1,566		)
Auction rate securities	—	—		—			177	102,810		(4,600		)	102,810		(4,600		)
Total	14	$	27,221	$	(191	)	459	$	1,217,852	$	(25,373	)	$	1,245,073	$	(25,564	)

No Held to Maturity investments were in an unrealized loss position at March 31, 2019.



	Less than 12 months						12 months or longer						Total
December 31, 2018	Number of Securities	Estimated Fair Value		Unrealized Losses			Number of Securities	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
Available for Sale	(in thousands)
U.S. Government sponsored agency securities	1	$	4,961	$	(31	)	1	$	5,770	$	(108	)	$	10,731	$	(139	)
State and municipal securities	33	72,950		(1,292		)	38	83,770		(4,174		)	156,720		(5,466		)
Corporate debt securities	8	24,419		(227		)	14	25,642		(3,126		)	50,061		(3,353		)
Collateralized mortgage obligations	39	136,563		(1,050		)	89	388,173		(10,922		)	524,736		(11,972		)
Residential mortgage-backed securities	17	18,220		(222		)	110	402,779		(14,990		)	420,999		(15,212		)
Commercial mortgage-backed securities	1	9,778		(35		)	25	197,326		(3,038		)	207,104		(3,073		)
Auction rate securities	—	—		—			177	102,994		(4,416		)	102,994		(4,416		)
Total	99	$	266,891	$	(2,857	)	454	$	1,206,454	$	(40,774	)	$	1,473,345	$	(43,631	)
Held to Maturity
State and municipal securities	6	$	20,601	$	(93	)	—	$	—	$	—		$	20,601	$	(93	)
Total	6	$	20,601	$	(93	)	—	$	—	$	—		$	20,601	$	(93	)

The Corporation’s collateralized mortgage obligations and mortgage-backed securities have contractual terms that generally do not permit the issuer to settle the securities at a price less than the amortized cost of the investment. The change in fair value of these securities is attributable to changes in interest rates and not credit quality, and the Corporation does not have the intent to sell and does not believe it will more likely than not be required to sell any of these securities prior to a recovery of their fair value to amortized cost. Therefore, the Corporation does not consider these investments to be other-than-temporarily impaired as of March 31, 2019.

As of March 31, 2019, all of the auction rate securities (auction rate certificates, or "ARCs") were rated above investment grade. Based on management’s evaluations, none of the ARCs were subject to any other-than-temporary impairment charges for the three months ended March 31, 2019. The Corporation does not have the intent to sell and does not believe it will more likely than not be required to sell any of these securities prior to a recovery of their fair value to amortized cost, which may be at maturity.

Based on management’s evaluations, no corporate debt securities were subject to any other-than-temporary impairment charges for the three months ended March 31, 2019. The Corporation does not have the intent to sell and does not believe it will more likely than not be required to sell any of these securities prior to a recovery of their fair value to amortized cost, which may be at maturity.