LOANS (covered) - Carrying Amount of Accretable Yield for Purchased Impaired and Nonimpaired Loans (Detail) (Covered Loans, USD $) In Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Covered Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	$ 421,781	[1]	$ 514,436	[1]	$ 509,945	[1]	$ 623,669	[1]
Reclassification from non-accretable difference	17,311		81,067		50,517		81,067
Accretion	(31,168)		(34,891)		(97,447)		(104,096)
Other net activity	(4,878)	[2]	(11,904)	[2]	(59,969)	[2]	(51,932)	[2]
Balance at end of period	$ 403,046		$ 548,708		$ 403,046		$ 548,708

[1] Excludes loans with revolving privileges which are scoped out of FASB Topic 310-30 and certain loans which First Financial elected to treat under the cost recovery method.

[2] Includes the impact of loan repayments and charge-offs.