Investment Securities - Reconciliation of Available-for-Sale and Held-to-Maturity Securities in Continuous Unrealized Loss Position (Detail) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015 USD ($) Security	Dec. 31, 2014 USD ($) Security
Investment [Line Items]
Available for Sale, Less than 12 months, Fair value	$ 150,911	$ 41,155
Available for Sale, Less than 12 months, Unrealized Losses	1,315	234
Available for Sale, 12 months or longer, Fair value	65,177	130,401
Available for Sale, 12 months or longer, Unrealized Losses	$ 1,634	$ 2,992
Available for Sale, Number of securities | Security	70	53
Available for Sale, Total, Fair value	$ 216,088	$ 171,556
Available for Sale, Total, Unrealized Losses	2,949	3,226
Held to Maturity, Less than 12 months, Fair value	49,913	7,526
Held to Maturity, Less than 12 months, Unrealized Losses	690	57
Held to Maturity, 12 months or longer, Fair value	9,868	29,698
Held to Maturity, 12 months or longer, Unrealized Losses	$ 288	$ 562
Held to Maturity, Number of securities | Security	43	24
Held to Maturity, Total, Fair value	$ 59,781	$ 37,224
Held to Maturity, Total, Unrealized Losses	978	619
US Treasury and Government Agencies [Member]
Investment [Line Items]
Available for Sale, Less than 12 months, Fair value	60,180	5,057
Available for Sale, Less than 12 months, Unrealized Losses	571	28
Available for Sale, 12 months or longer, Fair value	3,978	46,135
Available for Sale, 12 months or longer, Unrealized Losses	$ 22	$ 779
Available for Sale, Number of securities | Security	13	11
Available for Sale, Total, Fair value	$ 64,158	$ 51,192
Available for Sale, Total, Unrealized Losses	593	807
Held to Maturity, Less than 12 months, Fair value	15,688
Held to Maturity, Less than 12 months, Unrealized Losses	$ 164
Held to Maturity, 12 months or longer, Fair value		5,736
Held to Maturity, 12 months or longer, Unrealized Losses		$ 84
Held to Maturity, Number of securities | Security	3	1
Held to Maturity, Total, Fair value	$ 15,688	$ 5,736
Held to Maturity, Total, Unrealized Losses	164	84
Mortgage-Backed Securities, Residential [Member]
Investment [Line Items]
Available for Sale, Less than 12 months, Fair value	78,644	34,832
Available for Sale, Less than 12 months, Unrealized Losses	537	177
Available for Sale, 12 months or longer, Fair value	54,895	74,414
Available for Sale, 12 months or longer, Unrealized Losses	$ 1,278	$ 1,898
Available for Sale, Number of securities | Security	37	28
Available for Sale, Total, Fair value	$ 133,539	$ 109,246
Available for Sale, Total, Unrealized Losses	1,815	2,075
Held to Maturity, Less than 12 months, Fair value	16,372	6,236
Held to Maturity, Less than 12 months, Unrealized Losses	189	50
Held to Maturity, 12 months or longer, Fair value	7,382	17,557
Held to Maturity, 12 months or longer, Unrealized Losses	$ 183	$ 335
Held to Maturity, Number of securities | Security	9	8
Held to Maturity, Total, Fair value	$ 23,754	$ 23,793
Held to Maturity, Total, Unrealized Losses	372	385
Mortgage-Backed Securities, Multifamily [Member]
Investment [Line Items]
Available for Sale, Less than 12 months, Fair value	5,235
Available for Sale, Less than 12 months, Unrealized Losses	$ 68
Available for Sale, Number of securities | Security	1
Available for Sale, Total, Fair value	$ 5,235
Available for Sale, Total, Unrealized Losses	68
Held to Maturity, Less than 12 months, Fair value	1,259
Held to Maturity, Less than 12 months, Unrealized Losses	12
Held to Maturity, 12 months or longer, Fair value	887	2,199
Held to Maturity, 12 months or longer, Unrealized Losses	$ 51	$ 60
Held to Maturity, Number of securities | Security	2	2
Held to Maturity, Total, Fair value	$ 2,146	$ 2,199
Held to Maturity, Total, Unrealized Losses	63	60
Obligations of States and Political Subdivisions [Member]
Investment [Line Items]
Available for Sale, Less than 12 months, Fair value	6,852	1,266
Available for Sale, Less than 12 months, Unrealized Losses	139	29
Available for Sale, 12 months or longer, Fair value	1,436	5,033
Available for Sale, 12 months or longer, Unrealized Losses	$ 93	$ 104
Available for Sale, Number of securities | Security	17	12
Available for Sale, Total, Fair value	$ 8,288	$ 6,299
Available for Sale, Total, Unrealized Losses	232	133
Held to Maturity, Less than 12 months, Fair value	16,594	1,290
Held to Maturity, Less than 12 months, Unrealized Losses	325	7
Held to Maturity, 12 months or longer, Fair value	1,599	4,206
Held to Maturity, 12 months or longer, Unrealized Losses	$ 54	$ 83
Held to Maturity, Number of securities | Security	29	13
Held to Maturity, Total, Fair value	$ 18,193	$ 5,496
Held to Maturity, Total, Unrealized Losses	379	90
Equity Securities [Member]
Investment [Line Items]
Available for Sale, 12 months or longer, Fair value	4,868	4,819
Available for Sale, 12 months or longer, Unrealized Losses	$ 241	$ 211
Available for Sale, Number of securities | Security	2	2
Available for Sale, Total, Fair value	$ 4,868	$ 4,819
Available for Sale, Total, Unrealized Losses	$ 241	$ 211