Investment Securities (Tables)

3 Months Ended

Mar. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Available-for-sale Securities

The following is a summary of the amortized cost and fair value of investment securities available-for-sale and investment securities held-to-maturity at March 31, 2017 and December 31, 2016:

	Investment Securities Available-for-Sale
(Dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
March 31, 2017
U.S. Treasury securities	$	5,792	$	1	$	—	$	5,793
Government sponsored agencies	225,993		153		1,807		224,339
State and political subdivisions	309,518		140		9,249		300,409
Residential mortgage-backed securities	260,703		45		4,204		256,544
Collateralized mortgage obligations	371,084		75		3,838		367,321
Corporate bonds	90,438		27		1,212		89,253
Preferred stock and trust preferred securities	31,426		1,042		281		32,187
Total	$	1,294,954	$	1,483	$	20,591	$	1,275,846
December 31, 2016
U.S. Treasury securities	$	5,788	$	5	$	—	$	5,793
Government sponsored agencies	216,890		189		2,068		215,011
State and political subdivisions	311,704		163		11,779		300,088
Residential mortgage-backed securities	276,162		112		3,992		272,282
Collateralized mortgage obligations	323,965		63		4,003		320,025
Corporate bonds	90,859		16		1,401		89,474
Preferred stock and trust preferred securities	31,353		1,018		80		32,291
Total	$	1,256,721	$	1,566	$	23,323	$	1,234,964

Held-to-maturity Securities

	Investment Securities Held-to-Maturity
(Dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
March 31, 2017
State and political subdivisions	$	646,692	$	3,830	$	11,072	$	639,450
Trust preferred securities	500		—		150		350
Total	$	647,192	$	3,830	$	11,222	$	639,800
December 31, 2016
State and political subdivisions	$	622,927	$	2,648	$	17,354	$	608,221
Trust preferred securities	500		—		190		310
Total	$	623,427	$	2,648	$	17,544	$	608,531

Proceeds from sales of securities and the associated gains and losses recorded in earnings

Proceeds from sales of securities and the associated gains and losses recorded in earnings are listed below:

	For the three months ended March 31,
(Dollars in thousands)	2017		2016
Proceeds	$	—	$	644
Gross gains	90		19

Amortized cost and fair value of debt securities by contractual maturity

The following is a summary of the amortized cost and fair value of investment securities at March 31, 2017, by maturity, for both available-for-sale and held-to-maturity investment securities. The maturities of residential mortgage-backed securities and collateralized mortgage obligations are based on scheduled principal payments. The maturities of all other debt securities are based on final contractual maturity.

	March 31, 2017
(Dollars in thousands)	Amortized Cost		Fair Value
Investment Securities Available-for-Sale:
Due in one year or less	$	248,015	$	246,683
Due after one year through five years	529,893		524,707
Due after five years through ten years	347,825		340,248
Due after ten years	167,832		162,405
Preferred stock	1,389		1,803
Total	$	1,294,954	$	1,275,846
Investment Securities Held-to-Maturity:
Due in one year or less	$	70,242	$	70,210
Due after one year through five years	271,055		268,753
Due after five years through ten years	146,712		144,004
Due after ten years	159,183		156,833
Total	$	647,192	$	639,800

Summary of continuous unrealized loss position of securities

The following schedule summarizes information for both available-for-sale and held-to-maturity investment securities with gross unrealized losses at March 31, 2017 and December 31, 2016, aggregated by category and length of time that individual securities have been in a continuous unrealized loss position. As of March 31, 2017, the Corporation’s securities portfolio consisted of 2,309 securities, 1,418 of which were in an unrealized loss position.

	Less Than 12 Months				12 Months or More				Total
(Dollars in thousands)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
March 31, 2017
Government sponsored agencies	$	108,300	$	1,445	$	11,203	$	362	$	119,503	$	1,807
State and political subdivisions	705,870		19,603		26,084		718		731,954		20,321
Residential mortgage-backed securities	248,111		4,204		—		—		248,111		4,204
Collateralized mortgage obligations	311,566		3,626		12,528		212		324,094		3,838
Corporate bonds	78,815		1,211		1,499		1		80,314		1,212
Trust preferred securities	10,511		281		350		150		10,861		431
Total	$	1,463,173	$	30,370	$	51,664	$	1,443	$	1,514,837	$	31,813
December 31, 2016
Government sponsored agencies	$	105,702	$	1,707	$	15,023	$	361	$	120,725	$	2,068
State and political subdivisions	758,063		28,158		26,810		975		784,873		29,133
Residential mortgage-backed securities	244,239		3,992		—		—		244,239		3,992
Collateralized mortgage obligations	279,001		3,778		14,754		225		293,755		4,003
Corporate bonds	80,536		1,401		—		—		80,536		1,401
Trust preferred securities	10,699		80		310		190		11,009		270
Total	$	1,478,240	$	39,116	$	56,897	$	1,751	$	1,535,137	$	40,867