Investment securities (Tables)

6 Months Ended

Jun. 30, 2018

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 June 30, 2018 and December 31, 2017 are shown below:

	June 30, 2018
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Investment Securities
Available-for-sale debt securities
U.S. government agency securities	$	999	$	—	$	(16	)	$	983
Mortgage-backed securities - residential		494,599		169		(16,794	)		477,974
Municipals, tax exempt		122,710		1,472		(1,935	)		122,247
Treasury securities		7,364		—		(208	)		7,156
Total	$	625,672	$	1,641	$	(18,953	)	$	608,360

	December 31, 2017
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Investment Securities
Available-for-sale debt securities
U.S. government agency securities	$	999	$	—	$	(13	)	$	986
Mortgage-backed securities - residential		425,557		374		(7,150	)		418,781
Municipals, tax exempt		107,127		2,692		(568	)		109,251
Treasury securities		7,345		—		(93	)		7,252
Total debt securities		541,028		3,066		(7,824	)		536,270
Equity and other securities		7,870		1		(149	)		7,722
Total investment securities	$	548,898	$	3,067	$	(7,973	)	$	543,992

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.

	June 30, 2018				December 31, 2017
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	11,991	$	12,195	$	905	$	925
Due in one to five years		20,026		20,083		28,332		28,878
Due in five to ten years		18,795		18,769		19,218		19,588
Due in over ten years		80,261		79,339		67,016		68,098
		131,073		130,386		115,471		117,489
Mortgage-backed securities - residential		494,599		477,974		425,557		418,781
Total debt securities	$	625,672	$	608,360	$	541,028	$	536,270

Summary of Sales of Available-for-Sale Securities

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Proceeds from sales	$	—	$	12,158	$	221		12,158
Gross realized gains		—		77		—		77
Gross realized losses		—		48		9		48

Schedule of Gross Unrealized Losses

The following tables show gross unrealized losses at June 30, 2018 and December 31, 2017, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	June 30, 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	$	—	$	—	$	983	$	16	$	983	$	16
Mortgage-backed securities - residential		185,980		4,472		261,675		12,322		447,655		16,794
Municipals, tax exempt		32,413		760		19,158		1,175		51,571		1,935
Treasury securities		7,156		208		—		—		7,156	$	208
Total debt securities	$	225,549	$	5,440	$	281,816	$	13,513	$	507,365	$	18,953

	December 31, 2017
	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	$	—	$	—	$	986	$	13	$	986	$	13
Mortgage-backed securities - residential		107,611		980		290,258		6,170		397,869		7,150
Municipals, tax exempt		7,354		101		20,112		467		27,466		568
Treasury securities		7,252		93		—		—		7,252		93
Total debt securities		122,217		1,174		311,356		6,650		433,573		7,824
Equity and other securities		—		—		3,050		149		3,050		149
	$	122,217	$	1,174	$	314,406	$	6,799	$	436,623	$	7,973