Securities - Estimated Fair Value and Unrealized Loss for Securities Available-for-Sale and Held-to-Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Total securities, Less than 12 months, Estimated Fair Value	$ 13,714	$ 127,789
Total securities, Less than 12 months, Unrealized Losses	(9)	(706)
Total securities, 12 months or longer, Estimated Fair Value	86,971	129,057
Total securities, 12 months or longer, Unrealized Losses	(9,863)	(10,522)
Total securities, Estimated Fair Value	100,685	256,846
Total securities, Unrealized Losses	(9,872)	(11,228)
Held-to-Maturity Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, Less than 12 months, Estimated Fair Value	9,712	112,852
Held-to-maturity, Less than 12 months, Unrealized Losses	(6)	(679)
Held-to-maturity, 12 months or longer, Estimated Fair Value	86,971	129,057
Held-to-maturity, 12 months or longer, Unrealized Losses	(9,863)	(10,522)
Held-to-maturity, Total, Estimated Fair Value	96,683	241,909
Held-to-maturity, Total, Unrealized Losses	(9,869)	(11,201)
Held-to-Maturity Securities [Member] | Investment Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, Less than 12 months, Estimated Fair Value	3,619	33,032
Held-to-maturity, Less than 12 months, Unrealized Losses	(2)	(45)
Held-to-maturity, 12 months or longer, Estimated Fair Value	45,681	52,135
Held-to-maturity, 12 months or longer, Unrealized Losses	(9,595)	(8,544)
Held-to-maturity, Total, Estimated Fair Value	49,300	85,167
Held-to-maturity, Total, Unrealized Losses	(9,597)	(8,589)
U.S. Agency Obligations [Member] | Investment Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Available-for-sale, Less than 12 months, Estimated Market Value	4,002	14,937
Available-for-sale, Less than 12 months, Unrealized Losses	(3)	(27)
Available-for-sale, 12 months or longer, Estimated Market Value	0	0
Available-for-sale, 12 months or longer, Unrealized Losses	0	0
Available-for-sale, Total, Estimated Market Value	4,002	14,937
Available-for-sale, Total, Unrealized Losses	(3)	(27)
U.S. Agency Obligations [Member] | Held-to-Maturity Securities [Member] | Investment Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, Less than 12 months, Estimated Fair Value		30,175
Held-to-maturity, Less than 12 months, Unrealized Losses		(43)
Held-to-maturity, 12 months or longer, Estimated Fair Value		5,023
Held-to-maturity, 12 months or longer, Unrealized Losses		(16)
Held-to-maturity, Total, Estimated Fair Value		35,198
Held-to-maturity, Total, Unrealized Losses		(59)
State and Municipal Obligations [Member] | Held-to-Maturity Securities [Member] | Investment Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, Less than 12 months, Estimated Fair Value	1,076	2,857
Held-to-maturity, Less than 12 months, Unrealized Losses	(1)	(2)
Held-to-maturity, 12 months or longer, Estimated Fair Value	275	639
Held-to-maturity, 12 months or longer, Unrealized Losses	(1)	(1)
Held-to-maturity, Total, Estimated Fair Value	1,351	3,496
Held-to-maturity, Total, Unrealized Losses	(2)	(3)
Corporate Debt Securities [Member] | Held-to-Maturity Securities [Member] | Investment Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, Less than 12 months, Estimated Fair Value	2,543
Held-to-maturity, Less than 12 months, Unrealized Losses	(1)
Held-to-maturity, 12 months or longer, Estimated Fair Value	45,406	46,473
Held-to-maturity, 12 months or longer, Unrealized Losses	(9,594)	(8,527)
Held-to-maturity, Total, Estimated Fair Value	47,949	46,473
Held-to-maturity, Total, Unrealized Losses	(9,595)	(8,527)
Mortgage-Backed Securities [Member] | Held-to-Maturity Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, Less than 12 months, Estimated Fair Value	6,093	79,820
Held-to-maturity, Less than 12 months, Unrealized Losses	(4)	(634)
Held-to-maturity, 12 months or longer, Estimated Fair Value	41,290	76,922
Held-to-maturity, 12 months or longer, Unrealized Losses	(268)	(1,978)
Held-to-maturity, Total, Estimated Fair Value	47,383	156,742
Held-to-maturity, Total, Unrealized Losses	(272)	(2,612)
Mortgage-Backed Securities [Member] | Held-to-Maturity Securities [Member] | FHLMC [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, Less than 12 months, Estimated Fair Value	1,834	35,816
Held-to-maturity, Less than 12 months, Unrealized Losses	(1)	(200)
Held-to-maturity, 12 months or longer, Estimated Fair Value	30,978	53,604
Held-to-maturity, 12 months or longer, Unrealized Losses	(167)	(1,289)
Held-to-maturity, Total, Estimated Fair Value	32,812	89,420
Held-to-maturity, Total, Unrealized Losses	(168)	(1,489)
Mortgage-Backed Securities [Member] | Held-to-Maturity Securities [Member] | FNMA [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, Less than 12 months, Estimated Fair Value	4,259	44,004
Held-to-maturity, Less than 12 months, Unrealized Losses	(3)	(434)
Held-to-maturity, 12 months or longer, Estimated Fair Value	10,312	23,318
Held-to-maturity, 12 months or longer, Unrealized Losses	(101)	(689)
Held-to-maturity, Total, Estimated Fair Value	14,571	67,322
Held-to-maturity, Total, Unrealized Losses	$ (104)	$ (1,123)