Investment Securities - Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Due in one year or less	$ 9,755
Due after one through five years	27,096
Due after five through ten years	50,169
Due after ten years	169,823
Available-For-Sale Securities, Debt Maturity, with Single Maturity Date, Amortized Cost, Total	256,843
Total Investment Securities	537,848
Due in one year or less	9,912
Due after one through five years	27,606
Due after five through ten years	50,739
Due after ten years	164,986
Available-For-Sale Securities, Debt Maturity, with Single Maturity Date, Fair Value, Total	253,243
Total Investment Securities	536,201
Due in one year or less	4,446
Due after one through five years	17,129
Due after five through ten years	77,012
Due after ten years	47,354
Held-To-Maturity Securities, Debt Maturities, with Single Maturity Date, Net Carrying Amount, Total	145,941
Amortized Cost	559,378	361,020
Due in one year or less	4,442
Due after one through five years	17,324
Due after five through ten years	76,860
Due after ten years	47,286
Held-To-Maturity Securities, Debt Maturity, with Single Maturity Date, Fair Value, Total	145,912
Total Investment Securities	560,847	378,174
U.S. Government-sponsored mortgage-backed securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Without single maturity date	279,299
Without single maturity date	281,252
Amortized Cost	413,437	243,793
Total Investment Securities	414,935	255,459
Equity securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Without single maturity date	1,706
Without single maturity date	$ 1,706