Securities - Amortized Cost, Gross Unrealized Gains and Losses and Estimated Fair Value of Securities Classified as Available for Sale and Held to Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available for Sale Securities, Amortized Cost	$ 550,785	$ 444,243
Available for Sale Securities, Gross Unrealized Gains	4,406	8,855
Available for Sale Securities, Gross Unrealized Losses	12,993	8,028
Available for Sale Securities, Estimated Fair Value	542,198	445,070
Held To Maturity Securities, Amortized Cost	6,238	10,225
Held To Maturity Securities, Gross Unrealized Gains	318	600
Held To Maturity Securities, Gross Unrealized Losses
Held To Maturity Securities, Estimated Fair Value	6,556	10,825
Mortgage-Backed Securities-Residential [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available for Sale Securities, Amortized Cost	349,216	290,063
Available for Sale Securities, Gross Unrealized Gains	2,211	5,337
Available for Sale Securities, Gross Unrealized Losses	11,732	312
Available for Sale Securities, Estimated Fair Value	339,695	295,088
Held To Maturity Securities, Amortized Cost	3,133	5,083
Held To Maturity Securities, Gross Unrealized Gains	249	415
Held To Maturity Securities, Gross Unrealized Losses
Held To Maturity Securities, Estimated Fair Value	3,382	5,498
Obligations of States and Political Subdivisions [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available for Sale Securities, Amortized Cost	87,884	79,638
Available for Sale Securities, Gross Unrealized Gains	1,520	2,974
Available for Sale Securities, Gross Unrealized Losses	100	10
Available for Sale Securities, Estimated Fair Value	89,304	82,602
Held To Maturity Securities, Amortized Cost	3,105	5,142
Held To Maturity Securities, Gross Unrealized Gains	69	185
Held To Maturity Securities, Gross Unrealized Losses
Held To Maturity Securities, Estimated Fair Value	3,174	5,327
U.S. Treasury and Government Agencies [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available for Sale Securities, Amortized Cost	94,427	53,197
Available for Sale Securities, Gross Unrealized Gains	35	36
Available for Sale Securities, Gross Unrealized Losses	770	10
Available for Sale Securities, Estimated Fair Value	93,692	53,223
Other Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available for Sale Securities, Amortized Cost	9,529	11,319
Available for Sale Securities, Gross Unrealized Gains	4	1
Available for Sale Securities, Gross Unrealized Losses	4	7,572
Available for Sale Securities, Estimated Fair Value	9,529	3,748
Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available for Sale Securities, Amortized Cost	541,056	434,217
Available for Sale Securities, Gross Unrealized Gains	3,770	8,348
Available for Sale Securities, Gross Unrealized Losses	12,606	7,904
Available for Sale Securities, Estimated Fair Value	532,220	434,661
Mutual Funds and Other Equity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Available for Sale Securities, Amortized Cost	9,729	10,026
Available for Sale Securities, Gross Unrealized Gains	636	507
Available for Sale Securities, Gross Unrealized Losses	387	124
Available for Sale Securities, Estimated Fair Value	$ 9,978	$ 10,409