Investment securities (Tables)

9 Months Ended

Sep. 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 September 30, 2018 and December 31, 2017 are shown below:

	September 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	$	—	$	(15	)	$	984
Mortgage-backed securities - residential		488,087		58		(20,431	)		467,714
Municipals, tax exempt		132,450		950		(2,728	)		130,672
Treasury securities		7,374		—		(243	)		7,131
Total	$	628,910	$	1,008	$	(23,417	)	$	606,501

	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.

	September 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	$	13,523	$	13,683	$	905	$	925
Due in one to five years		18,420		18,316		28,332		28,878
Due in five to ten years		19,463		19,209		19,218		19,588
Due in over ten years		89,417		87,579		67,016		68,098
		140,823		138,787		115,471		117,489
Mortgage-backed securities - residential		488,087		467,714		425,557		418,781
Total debt securities	$	628,910	$	606,501	$	541,028	$	536,270

Summary of Sales of Available-for-Sale Securities

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Proceeds from sales	$	—	$	82,585	$	221		94,743
Gross realized gains		—		1,199		—		1,276
Gross realized losses		—		—		9		48

Schedule of Gross Unrealized Losses

The following tables show gross unrealized losses at September 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:

	September 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	$	—	$	—	$	984	$	15	$	984	$	15
Mortgage-backed securities - residential		137,314		2,925		322,378		17,506		459,692		20,431
Municipals, tax exempt		49,234		976		24,410		1,752		73,644		2,728
Treasury securities		—		—		7,131		243		7,131	$	243
Total debt securities	$	186,548	$	3,901	$	354,903	$	19,516	$	541,451	$	23,417

	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