Securities - Estimated Fair Value and Unrealized Loss of Securities Available-for-Sale and Held-to-Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Total securities, Less than 12 months, Estimated Fair Value	$ 33,618	$ 45,040
Total securities, Less than 12 months, Unrealized Losses	(134)	(140)
Total securities, 12 months or longer, Estimated Fair Value	166,555	234,393
Total securities, 12 months or longer, Unrealized Losses	(9,838)	(12,605)
Total securities, Estimated Fair Value	200,173	279,433
Total securities, Unrealized Losses	(9,972)	(12,745)
Investment Securities [Member] | U.S. Agency Obligations [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Available-for-sale, Less than 12 months, Estimated Market Value		19,804
Available-for-sale, Less than 12 months, Unrealized Losses		(96)
Available-for-sale, 12 months or longer, Estimated Market Value		0
Available-for-sale, 12 months or longer, Unrealized Losses		0
Available-for-sale, Total, Estimated Market Value		19,804
Available-for-sale, Total, Unrealized Losses		(96)
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	33,618	25,236
Held-to-maturity, Less than 12 months, Unrealized Losses	(134)	(44)
Held-to-maturity, 12 months or longer, Estimated Fair Value	166,555	234,393
Held-to-maturity, 12 months or longer, Unrealized Losses	(9,838)	(12,605)
Held-to-maturity, Total, Estimated Fair Value	200,173	259,629
Held-to-maturity, Total, Unrealized Losses	(9,972)	(12,649)
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	1,746	16,081
Held-to-maturity, Less than 12 months, Unrealized Losses	(5)	(10)
Held-to-maturity, 12 months or longer, Estimated Fair Value	53,338	72,486
Held-to-maturity, 12 months or longer, Unrealized Losses	(7,756)	(9,798)
Held-to-maturity, Total, Estimated Fair Value	55,084	88,567
Held-to-maturity, Total, Unrealized Losses	(7,761)	(9,808)
Held-to-Maturity Securities [Member] | Investment Securities [Member] | U.S. Agency Obligations [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, Less than 12 months, Estimated Fair Value		15,134
Held-to-maturity, Less than 12 months, Unrealized Losses		(9)
Held-to-maturity, 12 months or longer, Estimated Fair Value	5,059	25,409
Held-to-maturity, 12 months or longer, Unrealized Losses	(2)	(41)
Held-to-maturity, Total, Estimated Fair Value	5,059	40,543
Held-to-maturity, Total, Unrealized Losses	(2)	(50)
Held-to-Maturity Securities [Member] | Investment Securities [Member] | State and Municipal Obligations [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, Less than 12 months, Estimated Fair Value	1,746	947
Held-to-maturity, Less than 12 months, Unrealized Losses	(5)	(1)
Held-to-maturity, 12 months or longer, Estimated Fair Value	1,029	1,827
Held-to-maturity, 12 months or longer, Unrealized Losses	(4)	(7)
Held-to-maturity, Total, Estimated Fair Value	2,775	2,774
Held-to-maturity, Total, Unrealized Losses	(9)	(8)
Held-to-Maturity Securities [Member] | Investment Securities [Member] | Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, 12 months or longer, Estimated Fair Value	47,250	45,250
Held-to-maturity, 12 months or longer, Unrealized Losses	(7,750)	(9,750)
Held-to-maturity, Total, Estimated Fair Value	47,250	45,250
Held-to-maturity, Total, Unrealized Losses	(7,750)	(9,750)
Held-to-Maturity Securities [Member] | Mortgage-Backed 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	31,872	9,155
Held-to-maturity, Less than 12 months, Unrealized Losses	(129)	(34)
Held-to-maturity, 12 months or longer, Estimated Fair Value	113,217	161,907
Held-to-maturity, 12 months or longer, Unrealized Losses	(2,082)	(2,807)
Held-to-maturity, Total, Estimated Fair Value	145,089	171,062
Held-to-maturity, Total, Unrealized Losses	(2,211)	(2,841)
Held-to-Maturity Securities [Member] | Mortgage-Backed 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	9,832	9,155
Held-to-maturity, Less than 12 months, Unrealized Losses	(10)	(34)
Held-to-maturity, 12 months or longer, Estimated Fair Value	74,779	96,975
Held-to-maturity, 12 months or longer, Unrealized Losses	(1,270)	(1,625)
Held-to-maturity, Total, Estimated Fair Value	84,611	106,130
Held-to-maturity, Total, Unrealized Losses	(1,280)	(1,659)
Held-to-Maturity Securities [Member] | Mortgage-Backed 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	22,040
Held-to-maturity, Less than 12 months, Unrealized Losses	(119)
Held-to-maturity, 12 months or longer, Estimated Fair Value	38,438	64,932
Held-to-maturity, 12 months or longer, Unrealized Losses	(812)	(1,182)
Held-to-maturity, Total, Estimated Fair Value	60,478	64,932
Held-to-maturity, Total, Unrealized Losses	$ (931)	$ (1,182)