Securities - Estimated Fair Value and Unrealized Loss for Securities Available-for-Sale and Held-to-Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 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		$ 127,789
Total securities, Less than 12 months, Unrealized Losses		(706)
Total securities, 12 months or longer, Estimated Fair Value		129,057
Total securities, 12 months or longer, Unrealized Losses		(10,522)
Total securities, Estimated Fair Value		256,846
Total securities, Unrealized Losses		(11,228)
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		14,937
Available-for-sale, Less than 12 months, Unrealized Losses		(27)
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		14,937
Available-for-sale, Total, Unrealized Losses		(27)
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	$ 8,038	112,852
Held-to-maturity, Less than 12 months, Unrealized Losses	(4)	(679)
Held-to-maturity, 12 months or longer, Estimated Fair Value	108,874	129,057
Held-to-maturity, 12 months or longer, Unrealized Losses	(12,578)	(10,522)
Held-to-maturity, Total, Estimated Fair Value	116,912	241,909
Held-to-maturity, Total, Unrealized Losses	(12,582)	(11,201)
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	2,569	79,820
Held-to-maturity, Less than 12 months, Unrealized Losses	(1)	(634)
Held-to-maturity, 12 months or longer, Estimated Fair Value	64,870	76,922
Held-to-maturity, 12 months or longer, Unrealized Losses	(667)	(1,978)
Held-to-maturity, Total, Estimated Fair Value	67,439	156,742
Held-to-maturity, Total, Unrealized Losses	(668)	(2,612)
Held-to-Maturity Securities [Member] | FHLMC [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	2,569	35,816
Held-to-maturity, Less than 12 months, Unrealized Losses	(1)	(200)
Held-to-maturity, 12 months or longer, Estimated Fair Value	42,176	53,604
Held-to-maturity, 12 months or longer, Unrealized Losses	(410)	(1,289)
Held-to-maturity, Total, Estimated Fair Value	44,745	89,420
Held-to-maturity, Total, Unrealized Losses	(411)	(1,489)
Held-to-Maturity Securities [Member] | FNMA [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		44,004
Held-to-maturity, Less than 12 months, Unrealized Losses		(434)
Held-to-maturity, 12 months or longer, Estimated Fair Value	22,694	23,318
Held-to-maturity, 12 months or longer, Unrealized Losses	(257)	(689)
Held-to-maturity, Total, Estimated Fair Value	22,694	67,322
Held-to-maturity, Total, Unrealized Losses	(257)	(1,123)
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	5,469	33,032
Held-to-maturity, Less than 12 months, Unrealized Losses	(3)	(45)
Held-to-maturity, 12 months or longer, Estimated Fair Value	44,004	52,135
Held-to-maturity, 12 months or longer, Unrealized Losses	(11,911)	(8,544)
Held-to-maturity, Total, Estimated Fair Value	49,473	85,167
Held-to-maturity, Total, Unrealized Losses	(11,914)	(8,589)
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	5,026	30,175
Held-to-maturity, Less than 12 months, Unrealized Losses	(2)	(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	5,026	35,198
Held-to-maturity, Total, Unrealized Losses	(2)	(59)
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	443	2,857
Held-to-maturity, Less than 12 months, Unrealized Losses	(1)	(2)
Held-to-maturity, 12 months or longer, Estimated Fair Value	913	639
Held-to-maturity, 12 months or longer, Unrealized Losses	(2)	(1)
Held-to-maturity, Total, Estimated Fair Value	1,356	3,496
Held-to-maturity, Total, Unrealized Losses	(3)	(3)
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	43,091	46,473
Held-to-maturity, 12 months or longer, Unrealized Losses	(11,909)	(8,527)
Held-to-maturity, Total, Estimated Fair Value	43,091	46,473
Held-to-maturity, Total, Unrealized Losses	$ (11,909)	$ (8,527)