Investment Securities (Tables)

12 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Investment Securities Portfolio

The following table summarizes the amortized cost and fair value of the available-for-sale and held-to-maturity investment securities portfolio at December 31 and the corresponding amounts of unrealized gains and losses therein:

(dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
2016
Available-for-Sale
U.S. Treasury	$	6,963	$	140	$	—		$	7,103
U.S. government-sponsored entities and agencies		506,234		113		(12,391	)		493,956
Mortgage-backed securities - Agency		1,551,465		6,923		(33,369	)		1,525,019
States and political subdivisions		446,003		4,183		(13,502	)		436,684
Pooled trust preferred securities		17,011		—		(8,892	)		8,119
Other securities		331,001		1,074		(5,782	)		326,293
Total available-for-sale securities	$	2,858,677	$	12,433	$	(73,936	)	$	2,797,174
Held-to-Maturity
U.S. government-sponsored entities and agencies	$	40,131	$	427	$	—		$	40,558
Mortgage-backed securities - Agency		10,640		300		—			10,940
States and political subdivisions		694,319		38,915		(560	)		732,674
Total held-to-maturity securities	$	745,090	$	39,642	$	(560	)	$	784,172
2015
Available-for-Sale
U.S. Treasury	$	11,968	$	190	$	(8	)	$	12,150
U.S. government-sponsored entities and agencies		615,578		1,495		(3,523	)		613,550
Mortgage-backed securities - Agency		1,065,936		10,970		(10,545	)		1,066,361
States and political subdivisions		375,671		11,960		(335	)		387,296
Pooled trust preferred securities		17,320		—		(9,420	)		7,900
Other securities		337,590		1,151		(7,777	)		330,964
Total available-for-sale securities	$	2,424,063	$	25,766	$	(31,608	)	$	2,418,221
Held-to-Maturity
U.S. government-sponsored entities and agencies	$	142,864	$	2,899	$	—		$	145,763
Mortgage-backed securities - Agency		16,042		562		—			16,604
States and political subdivisions		713,205		53,848		(3	)		767,050
Total held-to-maturity securities	$	872,111	$	57,309	$	(3	)	$	929,417

Schedule of Proceeds from Sales or Calls and Realized Gain and Losses of Available-for-Sale Investment Securities and Other Securities

Proceeds from sales or calls of available-for-sale investment securities, the resulting realized gains and realized losses, and other securities gains or losses were as follows for the years ended December 31:

(dollars in thousands)	2016			2015			2014
Proceeds from sales of available-for-sale securities	$	243,312		$	343,486		$	214,912
Proceeds from calls of available-for-sale securities		635,624			404,277			123,141
Total	$	878,936		$	747,763		$	338,053
Realized gains on sales of available-for-sale securities	$	5,423		$	5,640		$	9,938
Realized gains on calls of available-for-sale securities		922			605			154
Realized losses on sales of available-for-sale securities		(450	)		(518	)		(128	)
Realized losses on calls of available-for-sale securities		(147	)		(15	)		(471	)
Other securities gains (1)		100			6			337
Net securities gains	$	5,848		$	5,718		$	9,830

(1) Other securities gains includes net realized gains or losses associated with trading securities and mutual funds.

Expected Maturities of Investment Securities Portfolio

Weighted average yield is based on amortized cost.

	At December 31, 2016
(dollars in thousands) Maturity	Amortized Cost		Fair Value		Weighted Average Yield
Available-for-Sale
Within one year	$	37,370	$	37,431		1.72	%
One to five years		320,815		318,852		2.18
Five to ten years		329,607		329,892		2.85
Beyond ten years		2,170,885		2,110,999		2.43
Total	$	2,858,677	$	2,797,174		2.44	%
Held-to-Maturity
Within one year	$	10,796	$	10,906		4.02	%
One to five years		74,451		77,228		4.71
Five to ten years		129,452		135,004		4.86
Beyond ten years		530,391		561,034		5.58
Total	$	745,090	$	784,172		5.35	%

Investment Securities with Unrealized Losses by Aggregated Major Security Type and Length of Time in Continuous Unrealized Loss Position

The following table summarizes the investment securities with unrealized losses at December 31 by aggregated major security type and length of time in a continuous unrealized loss position:

	Less than 12 months					12 months or longer					Total
(dollars in thousands)	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
2016
Available-for-Sale
U.S. Treasury	$	—	$	—		$	—	$	—		$	—	$	—
U.S. government-sponsored entities and agencies		432,192		(12,391	)		—		—			432,192		(12,391	)
Mortgage-backed securities - Agency		1,177,093		(30,295	)		57,636		(3,074	)		1,234,729		(33,369	)
States and political subdivisions		286,351		(13,247	)		4,919		(255	)		291,270		(13,502	)
Pooled trust preferred securities		—		—			8,119		(8,892	)		8,119		(8,892	)
Other securities		121,498		(2,734	)		126,539		(3,048	)		248,037		(5,782	)
Total available-for-sale	$	2,017,134	$	(58,667	)	$	197,213	$	(15,269	)	$	2,214,347	$	(73,936	)
Held-to-Maturity
States and political subdivisions	$	59,481	$	(560	)	$	—	$	—		$	59,481	$	(560	)
Total held-to-maturity	$	59,481	$	(560	)	$	—	$	—		$	59,481	$	(560	)
2015
Available-for-Sale
U.S. Treasury	$	6,505	$	(8	)	$	—	$	—		$	6,505	$	(8	)
U.S. government-sponsored entities and agencies		160,751		(1,492	)		122,581		(2,031	)		283,332		(3,523	)
Mortgage-backed securities - Agency		256,359		(3,444	)		239,047		(7,101	)		495,406		(10,545	)
States and political subdivisions		38,373		(161	)		5,137		(174	)		43,510		(335	)
Pooled trust preferred securities		—		—			7,900		(9,420	)		7,900		(9,420	)
Other securities		156,604		(2,717	)		126,661		(5,060	)		283,265		(7,777	)
Total available-for-sale	$	618,592	$	(7,822	)	$	501,326	$	(23,786	)	$	1,119,918	$	(31,608	)
Held-to-Maturity
States and political subdivisions	$	2,026	$	(3	)	$	—	$	—		$	2,026	$	(3	)
Total held-to-maturity	$	2,026	$	(3	)	$	—	$	—		$	2,026	$	(3	)

Trust Preferred Securities

The table below summarizes the relevant characteristics of our pooled trust preferred securities as well as our single issuer trust preferred securities that are included in the “other securities” category in this footnote. Each of the pooled trust preferred securities support a more senior tranche of security holders. All three pooled trust preferred securities have experienced credit defaults. However, two of these securities have excess subordination and are not other-than-temporarily impaired as a result of their class hierarchy, which provides more loss protection.

Trust preferred securities December 31, 2016 (dollars in thousands)	Class		Lowest Credit Rating (1)		Amortized Cost		Fair Value		Unrealized Gain/ (Loss)			Realized Losses 2016		# of Issuers Currently Performing/ Remaining		Actual Deferrals and Defaults as a % of Original Collateral			Expected Defaults as a % of Remaining Performing Collateral			Excess Subordination as a % of Current Performing Collateral
Pooled trust preferred securities:
Reg Div Funding 2004		B-2		D	$	3,111	$	251	$	(2,860	)	$	—		21/38		34.7	%		8.4	%		0.0	%
Pretsl XXVII LTD		B		B		4,422		2,333		(2,089	)		—		35/44		16.7	%		12.2	%		32.3	%
Trapeza Ser 13A		A2A		BBB		9,478		5,535		(3,943	)		—		50/55		4.5	%		8.3	%		49.7	%
						17,011		8,119		(8,892	)		—
Single Issuer trust preferred securities:
Fleet Cap Tr V (BOA)				BB+		3,397		3,045		(352	)		—
JP Morgan Chase Cap XIII				BBB-		4,767		4,369		(398	)		—
NB-Global				BB+		786		905		119			—
Chase Cap II				BBB-		822		891		69			—
						9,772		9,210		(562	)		—
Total					$	26,783	$	17,329	$	(9,454	)	$	—

(1) Lowest rating for the security provided by any nationally recognized credit rating agency.