Securities - Continuous Unrealized Losses (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Less than 12 Months
Fair Value	$ 184,327	$ 106,735
Unrealized Loss	(3,652)	(771)
12 Months or More
Fair Value	121,572	134,831
Unrealized Loss	(4,909)	(3,428)
Fair Value	305,899	241,566
Unrealized Loss	(8,561)	(4,199)
U.S. Gov’t sponsored entities
Less than 12 Months
Fair Value	61,537	55,696
Unrealized Loss	(1,544)	(540)
12 Months or More
Fair Value	34,545	34,754
Unrealized Loss	(496)	(368)
Fair Value	96,082	90,450
Unrealized Loss	(2,040)	(908)
State & political subdivisions
Less than 12 Months
Fair Value	31,791	15,890
Unrealized Loss	(419)	(69)
12 Months or More
Fair Value	4,057	4,104
Unrealized Loss	(288)	(245)
Fair Value	35,848	19,994
Unrealized Loss	(707)	(314)
Residential & multi-family mortgage
Less than 12 Months
Fair Value	78,726	30,144
Unrealized Loss	(1,549)	(153)
12 Months or More
Fair Value	57,279	63,699
Unrealized Loss	(2,680)	(1,729)
Fair Value	136,005	93,843
Unrealized Loss	(4,229)	(1,882)
Corporate notes and bonds
Less than 12 Months
Fair Value	5,216	5,005
Unrealized Loss	(46)	(9)
12 Months or More
Fair Value	4,755	9,042
Unrealized Loss	(245)	(453)
Fair Value	9,971	14,047
Unrealized Loss	(291)	(462)
Pooled SBA
Less than 12 Months
Fair Value	7,057	0
Unrealized Loss	(94)	0
12 Months or More
Fair Value	20,001	22,270
Unrealized Loss	(1,115)	(575)
Fair Value	27,058	22,270
Unrealized Loss	(1,209)	(575)
Other
Less than 12 Months
Fair Value	0	0
Unrealized Loss	0	0
12 Months or More
Fair Value	935	962
Unrealized Loss	(85)	(58)
Fair Value	935	962
Unrealized Loss	$ (85)	$ (58)