Junior Subordinated Debentures (Additional Information) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Nov. 13, 2012
Eight Point Eight Five Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Percentage of Notice of redemption to trustee	8.85%
Junior subordinated debentures, redeemable percentage	100.00%
Value of securities redeemed to trustee	$ 103,093,000
Percentage of debt securities redeemed as compare to principal amount	102.09%
Debt extinguishment costs	2,100,000
Redemption received on debt securities	3,100,000
Unamortized discount	400,000
Nine Point Seven Five Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Percentage of Notice of redemption to trustee		9.75%
Value of securities redeemed to trustee		15,464,000
Percentage of debt securities redeemed as compare to principal amount	100.975%
Debt extinguishment costs	100,000
Redemption received on debt securities	$ 500,000