Investment securities (Tables)

3 Months Ended

Mar. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Summary of Amortized Cost of Securities and Fair Values

The amortized cost of securities and their fair values at March 31, 2019 and December 31, 2018 are shown below:

	March 31, 2019
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Investment Securities
Available-for-sale debt securities
U.S. government agency securities	$	1,000	$	—	$	(7	)	$	993
Mortgage-backed securities - residential	516,917		2,407		(7,608		)	511,716
Municipals, tax exempt	144,142		3,904		(406		)	147,640
Treasury securities	7,394		—		(89		)	7,305
Total	$	669,453	$	6,311	$	(8,110	)	$	667,654

	December 31, 2018
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Investment Securities
Available-for-sale debt securities
U.S. government agency securities	$	1,000	$	—	$	(11	)	$	989
Mortgage-backed securities - residential	520,654		1,191		(13,265		)	508,580
Municipals, tax exempt	138,994		1,565		(1,672		)	138,887
Treasury securities	7,385		—		(143		)	7,242
Total	$	668,033	$	2,756	$	(15,091	)	$	655,698

Schedule of Amortized Cost and Fair Value of Debt Securities by Contractual Maturity

Therefore, mortgage-backed securities are not included in the maturity categories in the following maturity summary.

	March 31, 2019				December 31, 2018
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	11,682	$	11,772	$	15,883	$	16,028
Due in one to five years	13,498		13,506		13,806		13,740
Due in five to ten years	16,891		16,974		18,539		18,387
Due in over ten years	110,465		113,686		99,151		98,963
	152,536		155,938		147,379		147,118
Mortgage-backed securities - residential	516,917		511,716		520,654		508,580
Total debt securities	$	669,453	$	667,654	$	668,033	$	655,698

Summary of Sales of Available-for-Sale Securities

Sales of available-for-sale securities were as follows:

	Three Months Ended March 31,
	2019		2018
Proceeds from sales	$	1,758	$	221
Gross realized gains	1		—
Gross realized losses	7		9

Schedule of Gross Unrealized Losses

The following tables show gross unrealized losses at March 31, 2019 and December 31, 2018, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	March 31, 2019
	Less than 12 months					12 months or more					Total
	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized loss
U.S. government agency securities	$	—	$	—		$	993	$	(7	)	$	993	$	(7	)
Mortgage-backed securities - residential	4,913		(10		)	357,430		(7,598		)	362,343		(7,608		)
Municipals, tax exempt	—		—			21,580		(406		)	21,580		(406		)
Treasury securities	—		—			7,305		(89		)	7,305		(89		)
Total	$	4,913	$	(10	)	$	387,308	$	(8,100	)	$	392,221	$	(8,110	)

	December 31, 2018
	Less than 12 months					12 months or more					Total
	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized loss
U.S. government agency securities	$	—	$	—		$	989	$	(11	)	$	989	$	(11	)
Mortgage-backed securities - residential	60,347		(478		)	335,769		(12,787		)	396,116		(13,265		)
Municipals, tax exempt	27,511		(366		)	25,343		(1,306		)	52,854		(1,672		)
Treasury securities	—		—			7,242		(143		)	7,242		(143		)
Total	$	87,858	$	(844	)	$	369,343	$	(14,247	)	$	457,201	$	(15,091	)