LOANS (covered) - Covered Loan Delinquency, Excluding Loans Accounted for Under FASB ASC Topic 310-30 (Detail) (USD $)	Sep. 30, 2011		Dec. 31, 2010
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	$ 1,151,066,000		$ 1,481,493,000
Covered Loans | Loans Excluded from FASB ASC Topic 310-30
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days past due	1,386,000		1,848,000
60 - 89 days past due	424,000		934,000
> 90 days past due	13,210,000		17,093,000
Total Past due	15,020,000		19,875,000
Current	80,478,000		111,480,000
Total	95,498,000		131,355,000
> 90 days past due and still accruing	68,000		9,000
Covered Loans | Loans Excluded from FASB ASC Topic 310-30 | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days past due	266,000		880,000
60 - 89 days past due	251,000		419,000
> 90 days past due	7,347,000		13,764,000
Total Past due	7,864,000		15,063,000
Current	6,855,000		23,376,000
Total	14,719,000		38,439,000
> 90 days past due and still accruing	0		0
Covered Loans | Loans Excluded from FASB ASC Topic 310-30 | Real estate-commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days past due	579,000		225,000
60 - 89 days past due	0		62,000
> 90 days past due	3,754,000		1,896,000
Total Past due	4,333,000		2,183,000
Current	8,086,000		15,600,000
Total	12,419,000		17,783,000
> 90 days past due and still accruing	0		0
Covered Loans | Loans Excluded from FASB ASC Topic 310-30 | Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days past due	0		0
60 - 89 days past due	0		0
> 90 days past due	0		0
Total Past due	0		0
Current	1,156,000		1,511,000
Total	1,156,000		1,511,000
> 90 days past due and still accruing	0		0
Covered Loans | Loans Excluded from FASB ASC Topic 310-30 | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days past due	499,000		656,000
60 - 89 days past due	163,000		443,000
> 90 days past due	2,032,000		1,424,000
Total Past due	2,694,000		2,523,000
Current	60,439,000		63,931,000
Total	63,133,000		66,454,000
> 90 days past due and still accruing	0		0
Covered Loans | Loans Excluded from FASB ASC Topic 310-30 | All other
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 days past due	42,000		87,000
60 - 89 days past due	10,000		10,000
> 90 days past due	77,000		9,000
Total Past due	129,000		106,000
Current	3,942,000		7,062,000
Total	4,071,000		7,168,000
> 90 days past due and still accruing	68,000		9,000
Loans Excluded from FASB ASC Topic 310-30 | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	14,719,000	[1]	38,439,000	[1]
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	223,882,000		334,039,000
Loans Excluded from FASB ASC Topic 310-30 | Real estate-commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	12,419,000	[1]	17,783,000	[1]
Real estate-commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	687,392,000		855,725,000
Loans Excluded from FASB ASC Topic 310-30 | Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	1,156,000	[1]	1,511,000	[1]
Installment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	14,178,000		21,071,000
Loans Excluded from FASB ASC Topic 310-30 | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	63,133,000	[1]	66,454,000	[1]
Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	67,897,000		73,695,000
Loans Excluded from FASB ASC Topic 310-30 | All other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	4,071,000	[1]	7,168,000	[1]
All other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	4,071,000		7,168,000
Loans Excluded from FASB ASC Topic 310-30
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	$ 95,498,000	[1]	$ 131,355,000	[1]

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