COVERED ASSETS AND FDIC INDEMNIFICATION ASSET (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 item		Dec. 31, 2013		Dec. 31, 2012
Allowance for loan losses disclosures
The number of grades used for the loan risk rating system	8
Financing Receivable Allowance for Credit Losses Roll Forward
Provision for (reversal of) loan losses	$ 49,158		$ 22,364		$ 65,184
Covered Loans
Allowance for loan losses disclosures
Principal Balance	1,604,940	[1]	2,461,560	[2]
Covered Loans | Total
Financing Receivable Allowance for Credit Losses Roll Forward
Beginning balance	7,745		5,153		6,647
Provision for (reversal of) loan losses	5,033		4,028		5,016
Charge-offs	(10,836)		(1,436)		(6,510)
Recoveries	1,563
Ending balance	3,505		7,745		5,153
Ending balance allocated to:
Collectively evaluated for impairment	3,081	[3]	5,476	[4]	5,153	[5]
Acquired with deteriorated credit quality	424		2,269
Allowance on covered loans	3,505		7,745		5,153
Covered Loans | Covered Advances
Allowance for loan losses disclosures
Principal Balance	253,300		320,200
Financing Receivable Allowance for Credit Losses Roll Forward
Beginning balance	5,476	[4]	5,153		6,647
Provision for (reversal of) loan losses	6,878		1,759		5,016
Charge-offs	(10,836)		(1,436)		(6,510)
Recoveries	1,563
Ending balance	3,081	[3]	5,476	[4]	5,153
Ending balance allocated to:
Collectively evaluated for impairment	3,081	[3]	5,476	[4]	5,153
Allowance on covered loans	3,081	[3]	5,476	[4]	5,153
Covered Loans | PCI Covered Loans
Financing Receivable Allowance for Credit Losses Roll Forward
Beginning balance	2,269
Provision for (reversal of) loan losses	(1,845)		2,269
Ending balance	424		2,269
Ending balance allocated to:
Acquired with deteriorated credit quality	424		2,269
Allowance on covered loans	424		2,269
CRE | Covered Loans
Allowance for loan losses disclosures
Principal Balance	751,719		1,267,363
CRE | Covered Loans | Covered Advances
Allowance for loan losses disclosures
Principal Balance	59,400		46,700
Financing Receivable Allowance for Credit Losses Roll Forward
Ending balance	676		1,800		2,500
Ending balance allocated to:
Collectively evaluated for impairment	676		1,800
Allowance on covered loans	676		1,800		2,500
C&I | Covered Loans
Allowance for loan losses disclosures
Principal Balance	252,986		426,621
C&I | Covered Loans | Covered Advances
Allowance for loan losses disclosures
Principal Balance	154,800		230,600
Financing Receivable Allowance for Credit Losses Roll Forward
Ending balance	2,000		3,200		2,400
Ending balance allocated to:
Collectively evaluated for impairment	2,000		3,200
Allowance on covered loans	2,000		3,200		2,400
Residential | Covered Loans
Allowance for loan losses disclosures
Principal Balance	537,249		693,603
Residential | Covered Loans | Covered Advances
Allowance for loan losses disclosures
Principal Balance	11,800		12,000
Financing Receivable Allowance for Credit Losses Roll Forward
Ending balance	166		176		87
Ending balance allocated to:
Collectively evaluated for impairment	166		176
Allowance on covered loans	166		176		87
Consumer | Covered Loans | Covered Advances
Allowance for loan losses disclosures
Principal Balance	27,300		30,900
Financing Receivable Allowance for Credit Losses Roll Forward
Ending balance	223		341		194
Ending balance allocated to:
Collectively evaluated for impairment	223		341
Allowance on covered loans	$ 223		$ 341		$ 194

[1] Includes $253.3 million of covered advances comprised of $154.8 million, $59.4 million, $27.3 million and $11.8 million of C&I, CRE, consumer and residential loans, respectively.

[2] Includes $320.2 million of covered advances comprised of $230.6 million, $46.7 million, $30.9 million and $12.0 million of C&I, CRE, consumer and residential loans, respectively.

[3] Allowance for loan losses of $2.0 million, $676 thousand, $223 thousand and $166 thousand are allocated to C&I, CRE, consumer and residential loans, respectively.

[4] Allowance for loan losses of $3.2 million, $1.8 million, $341 thousand and $176 thousand are allocated to C&I, CRE, consumer and residential loans, respectively.

[5] Allowance for loan losses of $2.4 million, $2.5 million and $194 thousand and $87 thousand are allocated to C&I, CRE, consumer and residential loans, respectively