Covered Assets and FDIC Loss-sharing Asset (Narrative) (Details) (USD $)	3 Months Ended	9 Months Ended		15 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Payment Of Clawback If Losses Less Than Stated Levels, Period After Acquisition		10 years 45 days
Amount of estimated clawback liability	$ 3,800,000	$ 3,800,000		$ 3,800,000
Provision for loan and lease losses		34,506,000	4,962,000
Federal deposit insurance corporation loss-sharing indemnified assets	101,800,000	101,800,000		101,800,000
Federal deposit insurance corporation loss-sharing indemnified assets receivable	9,900,000	9,900,000		9,900,000
FDIC Loss-sharing Asset, Period Increase (Decrease)	18,700,000
Covered Loans [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Percentage of loss shared by FDIC	80.00%	80.00%		80.00%
FDIC Percentage Of Loss Recoveries	80.00%	80.00%		80.00%
Percentage of loss shared by FDIC When Loss Share Thresholds Met	95.00%	95.00%		95.00%
Percentage Of Loss Recoveries Shared By FDIC When Loss Share Thresholds Met	95.00%	95.00%		95.00%
Provision for loan and lease losses	(3,992,000)	23,381,000	2,312,000	433,000
Impairment expenses		26,000,000
Negative provision to adjust allowance for loss		$ 2,600,000
Covered Loans [Member] | Maximum [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loss Sharing Agreement Effective Years		10 years
Loss Recovery Provision Effective Years		10 years
Covered Loans [Member] | Minimum [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loss Sharing Agreement Effective Years		5 years
Loss Recovery Provision Effective Years		8 years