Investment Securities - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014 security position	Mar. 31, 2013	Dec. 31, 2013 position security
Schedule of Held-to-maturity Securities [Line Items]
Proceeds from maturities, calls and paydowns of securities available for sale	$ 44,462,000	$ 106,313,000
Available for sale investment securities	1,130,141,000		1,157,594,000
Investment securities held to maturity	357,602,000		357,500,000
Total number of all held to maturity and available for sale securities in an unrealized loss position	283		346
Proceeds from the sale of securities available for sale	740,000	7,395,000
Gross gains	2,000	481,000
Gross losses	0	0
Cumulative credit losses on security sold	365,000
Proceeds from calls on securities available for sale	896,000
Recognized gain on calls of securities	0
Recognized loss on calls of securities	0
Other-than-temporary impairment charges, net	0	0
Number of securities in an unrealized loss position	66		76
Amortized cost	1,128,221,000		1,162,332,000
Total number of all held to maturity and available for sale securities in an unrealized loss position below investment grade	2
Recognized gain on calls of securities held to maturity portfolio	13,000
Proceeds from the calls	6,395,000
Recognized loss on sale of securities held to maturity portfolio	0
Proceeds from sales of held-to-maturity securities	19,388,000	31,731,000
Proceeds from sale of securities held to maturity portfolio	0
Number of securities in an unrealized loss position	217		270
Other Than Temporary Impairment, Cumulative Credit Losses Recognized, Securities Sold	1,500,000
Available-for-sale Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Proceeds from maturities, calls and paydowns of securities available for sale	6,085,000
Gross losses	365,000
Private Label Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Number of securities in an unrealized loss position	4
Amortized cost	3,700,000
Unrealized losses	27,000
Held-to-maturity Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Recognized gain on calls of securities held to maturity portfolio		13,000
Recognized loss on calls of securities held to maturity portfolio		2,000
Proceeds from the calls		9,044,000
Held-to-maturity Securities [Member] | Nonperforming Financing Receivable [Member]
Schedule of Held-to-maturity Securities [Line Items]
Recognized gain on sale of securities held to maturity portfolio		19,000
Recognized loss on sale of securities held to maturity portfolio		0
Proceeds from sales of held-to-maturity securities		$ 524,000