Investment Securities (Tables)

3 Months Ended

Mar. 31, 2016

Investments, Debt and Equity Securities [Abstract]

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

The amortized cost and estimated fair value of investment securities available-for-sale and held-to-maturity at March 31, 2016 and December 31, 2015, are presented below:

(Dollars in thousands)	March 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Available-for-Sale
Corporate bonds	$	42,959	$	23	$	3,170	$	39,812
Mortgage-backed securities—residential issued by government sponsored entities	611,433		9,603		172		620,864
Industrial revenue bonds	3,239		10		—		3,249
Total	$	657,631	$	9,636	$	3,342	$	663,925
Held-to-Maturity
U.S. Government agencies	$	12,491	$	456	$	—	$	12,947
Corporate bonds	74,016		232		3,000		71,248
State and political subdivisions—tax exempt	10,533		601		—		11,134
State and political subdivisions—taxable	526		24		—		550
Mortgage-backed securities—residential issued by government sponsored entities	362,917		8,593		17		371,493
Total	$	460,483	$	9,906	$	3,017	$	467,372

(Dollars in thousands)	December 31, 2015
	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
Available-for-Sale
Corporate bonds	$	22,870	$	112	$	227	$	22,755
Mortgage-backed securities—residential issued by government sponsored entities	614,176		1,376		4,415		611,137
Industrial revenue bonds	3,409		28		—		3,437
Total	$	640,455	$	1,516	$	4,642	$	637,329
Held-to-Maturity
U.S. Government agencies	$	12,805	$	230	$	—	$	13,035
Corporate bonds	70,059		—		401		69,658
State and political subdivisions—tax exempt	10,849		488		—		11,337
State and political subdivisions—taxable	528		17		—		545
Mortgage-backed securities—residential issued by government sponsored entities	378,264		3,107		812		380,559
Total	$	472,505	$	3,842	$	1,213	$	475,134

Estimated Fair Value of Investment Securities Available for Sale and Held to Maturity by Contractual Maturity

The estimated fair value of investment securities at March 31, 2016, by contractual maturity, is shown in the table that follows. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations without call or prepayment penalties. Debt securities not due at a single maturity date are shown separately.

(Dollars in thousands)	March 31, 2016
	Amortized Cost		Estimated Fair Value		Yield
Available-for-sale
Due in one year or less	$	—	$	—	—	%
Due after one year through five years	—		—		—	%
Due after five years through ten years	—		—		—	%
Due after ten years	46,198		43,061		2.95	%
Mortgage-backed securities—residential issued by government sponsored entities	611,433		620,864		2.09	%
Total	$	657,631	$	663,925	2.14	%
	Amortized Cost		Estimated Fair Value		Yield
Held-to-maturity
Due in one year or less	$	—	$	—	—	%
Due after one year through five years	19,311		18,330		4.37	%
Due after five years through ten years	65,238		64,052		4.89	%
Due after ten years	13,017		13,497		2.87	%
Mortgage-backed securities—residential issued by government sponsored entities	362,917		371,493		2.40	%
Total	$	460,483	$	467,372	2.83	%

Securities with Unrealized Losses Not Recognized in Income

Securities with unrealized losses not recognized in income, and the period of time they have been in an unrealized loss position, are as follows:

(Dollars in thousands)	Less than 12 Months				12 Months or Longer				Total
March 31, 2016	Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
Available-for-Sale
Corporate bonds	$	35,791	$	3,170	$	—	$	—	$	35,791	$	3,170
Mortgage-backed securities—residential issued by government sponsored entities	43,975		76		30,090		96		74,065		172
Total	$	79,766	$	3,246	$	30,090	$	96	$	109,856	$	3,342
Held-to-Maturity
U.S. government agencies	$	—	$	—	$	12,947	$	100	$	12,947	$	100
Corporate bonds	41,391		2,571		4,625		429		46,016		3,000
Mortgage-backed securities—residential issued by government sponsored entities	27,033		128		122,880		546		149,913		674
Total	$	68,424	$	2,699	$	140,452	$	1,075	$	208,876	$	3,774

(Dollars in thousands)	Less than 12 Months				12 Months or Longer				Total
December 31, 2015	Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
Available-for-Sale
Corporate bonds	$	8,237	$	227	$	—	$	—	$	8,237	$	227
Mortgage-backed securities—residential issued by government sponsored entities	378,852		3,723		31,273		692		410,125		4,415
Total	$	387,089	$	3,950	$	31,273	$	692	$	418,362	$	4,642
Held-to-Maturity
Corporate bonds	$	—	$	—	$	13,035	$	351	$	13,035	$	351
U.S Government agencies	44,658		401		—		—		44,658		401
Mortgage-backed securities—residential issued by government sponsored entities	143,368		1,691		143,147		3,298		286,515		4,989
Total	$	188,026	$	2,092	$	156,182	$	3,649	$	344,208	$	5,741