Investment securities (Tables)

12 Months Ended

Dec. 31, 2016

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 December 31, 2016 and 2015 are shown below:

	December 31, 2016
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Securities Available-for-Sale
Debt securities
U.S. government agency securities	$	998	$	—	$	(13	)	$	985
Mortgage-backed securities - residential		450,874		939		(7,905	)		443,908
Municipals, tax exempt		116,034		3,003		(2,114	)		116,923
Treasury securities		11,809		—		(52	)		11,757
Total debt securities		579,715		3,942		(10,084	)		573,573
Equity securities		8,744		1		(135	)		8,610
Total securities available-for-sale	$	588,459	$	3,943	$	(10,219	)	$	582,183

	December 31, 2015
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Securities Available-for-Sale
Debt securities
U.S. government agency securities	$	34,161	$	—	$	(353	)	$	33,808
Mortgage-backed securities - residential		524,141		3,675		(5,443	)		522,373
Municipals, tax exempt		74,945		4,892		—			79,837
Treasury securities		4,507		—		(22	)		4,485
Total debt securities		637,754		8,567		(5,818	)		640,503
Equity securities		8,971	3			(90	)		8,884
Total securities available-for-sale	$	646,725	$	8,570	$	(5,908	)	$	649,387

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.

	Years Ended December 31,
	2016				2015
	Available-for-sale				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
Due in one year or less	$	9,290	$	9,352	$	6,849	$	6,886
Due in one to five		25,520		26,340		44,108		44,358
Due in five to ten years		31,122		32,248		29,964		31,927
Due in over ten years		62,909		61,725		32,692		34,959
		128,841		129,665		113,613		118,130
Mortgage-backed securities - residential		450,874		443,908		524,141		522,373
	$	579,715	$	573,573	$	637,754	$	640,503

Summary of Sales of Available-for-Sale Securities

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

	Years Ended December 31,
	2016		2015		2014
Proceeds from sales	$	271,148	$	194,611	$	68,900
Gross realized gains		4,755		1,844		2,000
Gross realized losses		348		—		—

Schedule of Gross Unrealized Losses

The following tables show gross unrealized losses at December 31, 2016 and 2015, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position:

	Year ended December 31, 2016
	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	$	985	$	13	$	—	$	—	$	985	$	13
Mortgage-backed securities - residential		390,595		7,230		19,073		675		409,668		7,905
Municipals, tax exempt		43,132		2,114		—		—		43,132		2,114
Treasury securities		10,256		52		—		—		10,256	$	52
Total debt securities		444,968		9,409		19,073		675		464,041		10,084
Equity securities		—		—		3,126		135		3,126		135
	$	444,968	$	9,409	$	22,199	$	810	$	467,167	$	10,219

	Year ended December 31, 2015
	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	$	15,887	$	124	$	17,921	$	229	$	33,808	$	353
Mortgage-backed securities - residential		219,756		1,778		121,362		3,665		341,118		5,443
Municipals, tax exempt		4,485		22		—		—		4,485		22
Total debt securities		240,128		1,924		139,283		3,894		379,411		5,818
Equity securities		—		—		1,583		90		1,583		90
	$	240,128	$	1,924	$	140,866	$	3,984	$	380,994	$	5,908