Investment Securities - Narrative (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Fair value	$ 477,132,000	$ 17,038,000
Gross Unrealized Losses	9,543,000	5,945,000
Gross Unrealized Losses	3,813,000	16,000
Amortized Cost	537,848,000	498,104,000
Carrying value of securities pledged as collateral	373,533,000	345,866,000	306,024,000
Gross gains	487,000	2,389,000	2,439,000
Gross losses	0	0	0
Minimum
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Spread over LIBOR	0.85%
Maximum
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Spread over LIBOR	1.57%
Investments in Debt and Equity Securities, Reported at Less than Historical Cost
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Historical cost	490,488,000	22,999,000
Fair value	477,132,000	17,038,000
Percent of the Corporation's available for sale and held to maturity portfolio	43.60%	1.90%
U.S. Treasury Securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Fair value	4,875,000
Gross Unrealized Losses	21,000
Available-for-sale, number of securities in unrealized loss positions	1
Amortized Cost	15,914,000
U.S. Government-sponsored agency securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Fair value	3,433,000
Gross Unrealized Losses	17,000
Available-for-sale, number of securities in unrealized loss positions	3
Amortized Cost	3,550,000	4,475,000
U.S. Government-sponsored mortgage-backed securities
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Fair value	336,237,000	12,320,000
Gross Unrealized Losses	1,973,000	46,000
Available-for-sale, number of securities in unrealized loss positions	26
Gross Unrealized Losses	3,722,000	15,000
Held-to-maturity, number of securities in unrealized loss positions	45
Amortized Cost	279,299,000	337,631,000
State and municipal
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Fair value	129,876,000	4,524,000
Gross Unrealized Losses	3,896,000	18,000
Available-for-sale, number of securities in unrealized loss positions	137
Gross Unrealized Losses	91,000	1,000
Held-to-maturity, number of securities in unrealized loss positions	41
Amortized Cost	231,005,000	148,187,000
Corporate obligations
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Fair value	2,711,000	194,000
Gross Unrealized Losses	3,636,000	5,881,000
Amortized Cost	$ 6,374,000	$ 6,105,000