Investment Securities - Summary of Amortized Cost and Estimated Market Values by Contractual Maturity of Investment Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Amortized Cost And Fair Value Debt Securities [Abstract]
Weighted average yield, Due in one year or less	1.39%	1.04%
Weighted average yield, Due after one year through five years	2.58%	1.96%
Weighted average yield, Due after five years through ten years	2.12%	2.36%
Weighted average yield, Due after ten years	3.17%	2.60%
Weighted average yield, Total securities	2.30%	1.67%
Weighted average yield, Due in one year or less	1.76%
Weighted average yield, Due after one year through five years	2.60%
Weighted average yield, Due after five years through ten years	3.70%
Weighted average yield, Due after ten years	3.41%
Weighted average yield, Total securities	3.35%
Amortized Cost, Due in one year or less	$ 12,340	$ 119,657
Amortized Cost, Due after one year through five years	64,790	106,676
Amortized Cost, Due after five years through ten years	180,362	130,396
Amortized Cost, Due after ten years	36,767	46,276
Amortized Cost, Total securities	294,259	403,005
Amortized Cost, Due in one year or less	1,007
Amortized Cost, Due after one year through five years	18,101
Amortized Cost, Due after five years through ten years	37,591
Amortized Cost, Due after ten years	38,205
Amortized Cost, Total securities	94,904
Estimated Market Value, Due in one year or less	12,368	119,753
Estimated Market Value, Due after one year through five years	65,038	108,349
Estimated Market Value, Due after five years through ten years	168,243	130,958
Estimated Market Value, Due after ten years	32,070	46,295
Estimated Market Value	277,719	405,355
Estimated Market Value, Due in one year or less	1,007
Estimated Market Value, Due after one year through five years	17,539
Estimated Market Value, Due after five years through ten years	37,137
Estimated Market Value, Due after ten years	35,283
Estimated Market Value, Total securities	$ 94,904