Regulatory Matters - Additional Information (Detail) (USD $)	1 Months Ended					3 Months Ended					9 Months Ended			1 Months Ended	9 Months Ended
	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	May 19, 2010	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2009	Oct. 31, 2013 Subsequent Event [Member]	Sep. 30, 2013 Installment One FY Two Thousand Thirteen [Member]	Sep. 30, 2013 Installment Two FY Two Thousand Thirteen [Member]	Sep. 30, 2013 Installment Three FY Two Thousand Thirteen [Member]	Sep. 30, 2013 Installment Four FY Two Thousand Thirteen [Member]	Sep. 30, 2013 Installment Five Fy Two Thousand Thirteen [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Trust preferred securities						$ 32,000,000			$ 32,000,000		$ 32,000,000
Aggregate amount of restricted core elements allowed in Tier 1 capital											25.00%
Trusted preferred securities issued date					before May 19, 2010
Maximum level of consolidated aggregate assets allowing for inclusion of trust preferred securities in Tier Capital under Dodd-Frank Act													$ 15,000,000,000
Cash dividend on common stock						$ 0.12	$ 0.11	$ 0.10	$ 0.09	$ 0.00	$ 0.33	$ 0.00
Cash dividend declared on common stock	$ 0.12	$ 0.11	$ 0.10	$ 0.09										$ 0.12
Dividend declared date															Oct. 11, 2012	Jan. 10, 2013	Apr. 11, 2013	Jul. 11, 2013	Oct. 10, 2013
Dividend payable date															Dec. 10, 2012	Mar. 08, 2013	Jun. 10, 2013	Sep. 10, 2013	Dec. 10, 2013
Dividend payable date of record															Nov. 09, 2012	Feb. 08, 2013	May 10, 2013	Aug. 09, 2013	Nov. 08, 2013
Dividend suspended date											Apr. 01, 2010