Securities Available for Sale - Scheduled Maturities of Securities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Available For Sale Securities Debt Maturities [Abstract]
Weighted Average Yield, Due in one year or less	3.74%	2.79%
Weighted Average Yield, Due from one year to five years	2.79%	2.97%
Weighted Average Yield, Due from five to ten years	3.42%	3.37%
Weighted Average Yield, Due after ten years	3.06%	3.14%
Weighted Average Yield, Total	3.08%	3.12%
Amortized cost, Due in one year or less	$ 39,789	$ 41,074
Amortized cost, Due from one year to five years	151,769	163,785
Amortized cost, Due from five to ten years	95,929	106,115
Amortized cost, Due after ten years	777,318	739,384
Amortized cost, Total	1,064,805	1,050,358
Fair value, Due in one year or less	40,436	41,497
Fair value, Due from one year to five years	156,561	169,767
Fair value, Due from five to ten years	99,642	107,917
Fair value, Due after ten years	795,262	741,914
Fair value, Total	$ 1,091,901	$ 1,061,095