Investment Securities

6 Months Ended

Jun. 30, 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
June 30, 2019	(in thousands)
Available for Sale
State and municipal securities	$	307,911	$	8,508	$	(85	)	$	316,334
Corporate debt securities	194,858		4,885		(2,321		)	197,422
Collateralized mortgage obligations	889,053		12,190		(2,126		)	899,117
Residential mortgage-backed securities	331,566		1,623		(3,914		)	329,275
Commercial mortgage-backed securities	433,027		7,406		(152		)	440,281
Auction rate securities	107,410		—		(4,045		)	103,365
Total	$	2,263,825	$	34,612	$	(12,643	)	$	2,285,794

Held to Maturity
State and municipal securities	$	155,861	$	8,700	$	—		$	164,561
Residential mortgage-backed securities	411,703		13,464		—			425,167
Total	$	567,564	$	22,164	$	—		$	589,728



	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 $857.1 million at June 30, 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 June 30, 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		$	5,828	$	5,828	$	—	$	—
Due from one year to five years		38,664		39,900		—		—
Due from five years to ten years		175,654		178,922		2,154		2,277
Due after ten years		390,033		392,471		153,707		162,284
		610,179		617,121		155,861		164,561
Residential mortgage-backed securities⁽¹⁾		331,566		329,275		411,703		425,167
Commercial mortgage-backed securities⁽¹⁾		433,027		440,281		—		—
Collateralized mortgage obligations⁽¹⁾		889,053		899,117		—		—
Total		$	2,263,825	$	2,285,794	$	567,564	$	589,728

(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 investment securities:



	Gross Realized Gains		Gross Realized Losses			Net Gains
Three months ended June 30, 2019	(in thousands)
Debt securities	$	3,012	$	(2,836	)	$	176
Total	$	3,012	$	(2,836	)	$	176
Three months ended June 30, 2018
Debt securities	$	1,530	$	(1,526	)	$	4
Total	$	1,530	$	(1,526	)	$	4

Six months ended June 30, 2019
Debt securities	$	3,269	$	(3,028	)	$	241
Total	$	3,269	$	(3,028	)	$	241
Six months ended June 30, 2018
Equity securities	$	9	$	—		$	9
Debt securities	1,540		(1,526		)	14
Total	$	1,549	$	(1,526	)	$	23

The following table presents a summary of the cumulative credit related other-than-temporary impairment charges, recognized as components of earnings, for debt securities held by the Corporation at June 30, 2019 and 2018:



	Three months ended June 30						Six months ended June 30
	2019			2018			2019			2018
	(in thousands)
Balance of cumulative credit losses on debt securities, beginning of period	$	(11,510	)	$	(11,510	)	$	(11,510	)	$	(11,510	)
Reductions for securities sold during the period	10,520			—			10,520			—
Balance of cumulative credit losses on debt securities, end of period	$	(990	)	$	(11,510	)	$	(990	)	$	(11,510	)

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 June 30, 2019 and December 31, 2018:



	Less than 12 months						12 months or longer						Total
June 30, 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	3	$	15,714	$	(44	)	4	$	17,403	$	(41	)	$	33,117	$	(85	)
Corporate debt securities	3	7,054		(8		)	14	25,988		(2,313		)	33,042		(2,321		)
Collateralized mortgage obligations	—	—		—			39	110,517		(2,126		)	110,517		(2,126		)
Residential mortgage-backed securities	—	—		—			61	285,675		(3,914		)	285,675		(3,914		)
Commercial mortgage-backed securities	1	11,926		(143		)	2	17,475		(9		)	29,401		(152		)
Auction rate securities	—	—		—			177	103,365		(4,045		)	103,365		(4,045		)
Total	7	$	34,694	$	(195	)	297	$	560,423	$	(12,448	)	$	595,117	$	(12,643	)

No Held to Maturity investments were in an unrealized loss position at June 30, 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 June 30, 2019.

As of June 30, 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 and six months ended June 30, 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 and six months ended June 30, 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.