Principal Changes in Fair Value as Previously Reported in Form 10-Qs Filed During 2010 and the Revised Amounts Recorded during the Measurement Period (Parenthetical) (Detail) (Federal Deposit Insurance Corporation)	1 Months Ended	3 Months Ended
	Apr. 30, 2010	Jun. 30, 2011	Mar. 31, 2011
Federal Deposit Insurance Corporation
Business Acquisition [Line Items]
FDIC loss sharing agreements, percentage	80.00%	80.00%	80.00%