Investment Securities Available-for-Sale (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Schedule of available-for-sale securities reconciliation

Amortized cost and estimated fair value of securities available-for-sale are summarized as follows:

			Gross		Gross		Estimated
December 31, 2017	Amortized		Unrealized		Unrealized		Fair
(dollars in thousands)	Cost		Gains		Losses		Value
U. S. agency securities	$	198,115	$	283	$	2,414	$	195,984
Residential mortgage backed securities	322,067		187		4,418		317,836
Municipal bonds	60,976		1,295		214		62,057
Corporate bonds	13,010		163		—		13,173
Other equity investments	218		—		—		218
	$	594,386	$	1,928	$	7,046	$	589,268

			Gross		Gross		Estimated
December 31, 2016	Amortized		Unrealized		Unrealized		Fair
(dollars in thousands)	Cost		Gains		Losses		Value
U. S. agency securities	$	107,425	$	519	$	1,802	$	106,142
Residential mortgage backed securities	329,606		324		3,691		326,239
Municipal bonds	94,607		1,723		400		95,930
Corporate bonds	9,508		82		11		9,579
Other equity investments	218		—		—		218
	$	541,364	$	2,648	$	5,904	$	538,108

Schedule of unrealized loss on investments

Gross unrealized losses and fair value by length of time that the individual available-for-sale securities have been in a continuous unrealized loss position as of December 31, 2017 and 2016 are as follows:

		Less than				12 Months
		12 Months				or Greater				Total
		Estimated				Estimated				Estimated
December 31, 2017	Number of	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(dollars in thousands)	Securities	Value		Losses		Value		Losses		Value		Losses
U. S. agency securities	38	$	102,264	$	1,073	$	55,093	$	1,341	$	157,357	$	2,414
Residential mortgage backed securities	137	152,350		1,306		147,953		3,112		300,303		4,418
Municipal bonds	8	17,446		214		—		—		17,446		214
	183	$	272,060	$	2,593	$	203,046	$	4,453	$	475,106	$	7,046

		Less than				12 Months
		12 Months				or Greater				Total
		Estimated				Estimated				Estimated
December 31, 2016	Number of	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
(dollars in thousands)	Securities	Value		Losses		Value		Losses		Value		Losses
U. S. agency securities	27	$	88,991	$	1,764	$	3,768	$	38	$	92,759	$	1,802
Residential mortgage backed securities	112	232,347		3,110		19,402		581		251,749		3,691
Municipal bonds	16	34,743		400		—		—		34,743		400
Corporate bonds	2	4,998		11		—		—		4,998		11
	157	$	361,079	$	5,285	$	23,170	$	619	$	384,249	$	5,904

Schedule of available-for-sale securities by contractual maturity

The amortized cost and estimated fair value of investments available-for-sale at December 31, 2017 and 2016 by contractual maturity are shown in the table below.

	December 31, 2017				December 31, 2016
	Amortized		Estimated		Amortized		Estimated
(dollars in thousands)	Cost		Fair Value		Cost		Fair Value
U. S. agency securities maturing:
One year or less	$	109,893	$	108,198	$	83,885	$	82,548
After one year through five years	74,106		73,916		20,736		20,897
Five years through ten years	14,116		13,870		2,804		2,697
Residential mortgage backed securities	322,067		317,836		329,606		326,239
Municipal bonds maturing:
One year or less	5,068		5,171		1,056		1,070
After one year through five years	19,405		19,879		45,808		46,865
Five years through ten years	35,432		35,846		46,668		46,839
After ten years	1,071		1,161		1,075		1,156
Corporate bonds
After one year through five years	11,510		11,673		8,008		8,079
After ten years	1,500		1,500		1,500		1,500
Other equity investments	218		218		218		218
	$	594,386	$	589,268	$	541,364	$	538,108