Regulatory Matters (Details Textual) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jul. 03, 2012	Dec. 31, 2011	Dec. 31, 2009	May 15, 2009
Regulatory matters (Additional Textual) [Abstract]
Total consolidated assets					$ 15,000,000,000
Outstanding balance of 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%
Issued Non Voting Preferred Stock to Treasury's Capital Purchase Program, Shares						616,438
Issued Non Voting Preferred Stock to Treasury's Capital Purchase Program, Per Share						$ 5.11
Repurchase price of warrant			7,500,000
Cash dividend paid by bank to parent company to fund the repurchase of the warrant	7,800,000
Reduction in retained earnings for accelerated discount on preferred stock	$ 7,500,000	$ 7,500,000
Dividend payable date		Jul. 02, 2012
Maximum [Member]
Regulatory Matters (Textual) [Abstract]
Decline in consolidated and bank's regulatory capital ratios, pro-forma basis	0.65%	0.65%
Minimum [Member]
Regulatory Matters (Textual) [Abstract]
Decline in consolidated and bank's regulatory capital ratios, pro-forma basis	0.55%	0.55%