Investment Securities - Schedule of Investment Securities' Gross Unrealized Losses and Fair Value by Investment Category (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less than 12 months, Fair Value	$ 430,729,000	$ 59,338,000
Available-for-sale securities, Less than 12 months, Unrealized Loss	4,710,000	236,000
Available-for-sale securities, 12 months or longer, Fair Value	32,938,000	271,416,000
Available-for-sale securities, 12 months or longer, Unrealized Loss	952,000	3,358,000
Available-for-sale securities, Total, Fair Value	463,667,000	330,754,000
Available-for-sale securities, Total, Unrealized Loss	5,662,000	3,594,000
Held-to-maturity, Less than 12 months, Fair Value	9,845,000
Held-to-maturity, Less than 12 months, Unrealized Loss	62,000
Held-to-maturity, 12 months or longer, Fair Value	0
Held-to-maturity, 12 months or longer, Unrealized Loss	0
Held-to-maturity, Total, Fair Value	9,845,000
Held-to-maturity, Total, Unrealized Loss	62,000	0
CMO [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less than 12 months, Fair Value	139,486,000	15,492,000
Available-for-sale securities, Less than 12 months, Unrealized Loss	1,703,000	108,000
Available-for-sale securities, 12 months or longer, Fair Value	26,536,000	61,630,000
Available-for-sale securities, 12 months or longer, Unrealized Loss	711,000	1,506,000
Available-for-sale securities, Total, Fair Value	166,022,000	77,122,000
Available-for-sale securities, Total, Unrealized Loss	2,414,000	1,614,000
FNMA MBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less than 12 months, Fair Value	214,465,000
Available-for-sale securities, Less than 12 months, Unrealized Loss	2,715,000
Available-for-sale securities, 12 months or longer, Fair Value		103,207,000
Available-for-sale securities, 12 months or longer, Unrealized Loss		1,106,000
Available-for-sale securities, Total, Fair Value	214,465,000	103,207,000
Available-for-sale securities, Total, Unrealized Loss	2,715,000	1,106,000
FHLMC MBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less than 12 months, Fair Value	41,791,000	23,901,000
Available-for-sale securities, Less than 12 months, Unrealized Loss	136,000	54,000
Available-for-sale securities, 12 months or longer, Fair Value	4,025,000	58,267,000
Available-for-sale securities, 12 months or longer, Unrealized Loss	177,000	478,000
Available-for-sale securities, Total, Fair Value	45,816,000	82,168,000
Available-for-sale securities, Total, Unrealized Loss	313,000	532,000
GNMA MBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less than 12 months, Fair Value	4,073,000
Available-for-sale securities, Less than 12 months, Unrealized Loss	29,000
Available-for-sale securities, 12 months or longer, Fair Value	2,377,000	48,312,000
Available-for-sale securities, 12 months or longer, Unrealized Loss	64,000	268,000
Available-for-sale securities, Total, Fair Value	6,450,000	48,312,000
Available-for-sale securities, Total, Unrealized Loss	93,000	268,000
GSE [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Less than 12 months, Fair Value	30,914,000	19,945,000
Available-for-sale securities, Less than 12 months, Unrealized Loss	127,000	74,000
Available-for-sale securities, Total, Fair Value	30,914,000	19,945,000
Available-for-sale securities, Total, Unrealized Loss	127,000	$ 74,000
State and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity, Less than 12 months, Fair Value	9,845,000
Held-to-maturity, Less than 12 months, Unrealized Loss	62,000
Held-to-maturity, 12 months or longer, Fair Value	0
Held-to-maturity, 12 months or longer, Unrealized Loss	0
Held-to-maturity, Total, Fair Value	9,845,000
Held-to-maturity, Total, Unrealized Loss	$ 62,000