Allowance for loan losses (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Noncovered Loans [Member]
Allowance for loan losses
Individually evaluated for impairment	$ 7,239	$ 7,080	$ 7,112
Collectively evaluated for impairment	96,610	100,619	107,578
Financing Receivable, Allowance for Credit Losses	103,849	107,699	114,690	114,690
Noncovered Loans [Member] | Commercial Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	(972)	(2,497)	(156)
Collectively evaluated for impairment	(36,200)	(29,866)	(31,493)
Financing Receivable, Allowance for Credit Losses	37,172	32,363	31,649	29,764
Noncovered Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	2,478	1,599	3,932
Collectively evaluated for impairment	25,300	30,258	29,196
Financing Receivable, Allowance for Credit Losses	27,778	31,857	33,128	32,026
Noncovered Loans [Member] | Commercial Construction Financing Receivable Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	224	99	1,622
Collectively evaluated for impairment	4,900	5,074	6,017
Financing Receivable, Allowance for Credit Losses	5,124	5,173	7,639	7,180
Noncovered Loans [Member] | Finance Leases Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	(334)	(341)	(480)
Financing Receivable, Allowance for Credit Losses	334	341	480	475
Noncovered Loans [Member] | Installment Financing Receivable Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	1,902	1,382	336
Collectively evaluated for impairment	12,851	16,599	20,373
Financing Receivable, Allowance for Credit Losses	14,753	17,981	20,709	21,555
Noncovered Loans [Member] | Home Equity Receivable Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	(66)	(31)	(8)
Collectively evaluated for impairment	(6,203)	(6,735)	(6,875)
Financing Receivable, Allowance for Credit Losses	6,269	6,766	6,883	7,217
Noncovered Loans [Member] | Credit Card Receivables Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	92	108	162
Collectively evaluated for impairment	6,428	7,261	8,550
Financing Receivable, Allowance for Credit Losses	6,520	7,369	8,712	11,107
Noncovered Loans [Member] | Residential Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	1,505	1,364	896
Collectively evaluated for impairment	4,394	4,485	4,594
Financing Receivable, Allowance for Credit Losses	5,899	5,849	5,490	5,366
Legacy Loans [Member]
Legacy Loans
Ending Balance: Individually Evaluated	105,156	111,610	96,242
Ending Balance: Collectively Evaluated	7,658,903	7,524,166	6,893,731
Total ending balance	7,764,059	7,635,776	6,989,973
Legacy Loans [Member] | Commercial Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated	6,079	8,269	4,629
Ending Balance: Collectively Evaluated	2,867,093	2,740,433	2,130,654
Total ending balance	2,873,172	2,748,702	2,135,283
Legacy Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated	32,112	36,087	53,551
Ending Balance: Collectively Evaluated	1,952,461	1,956,106	1,947,872
Total ending balance	1,984,573	1,992,193	2,001,423
Legacy Loans [Member] | Commercial Construction Financing Receivable Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated	8,929	9,320	12,555
Ending Balance: Collectively Evaluated	276,786	268,015	246,463
Total ending balance	285,715	277,335	259,018
Legacy Loans [Member] | Finance Leases Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated	0	0	0
Ending Balance: Collectively Evaluated	74,112	73,530	60,487
Total ending balance	74,112	73,530	60,487
Legacy Loans [Member] | Installment Financing Receivable Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated	32,378	33,571	8,333
Ending Balance: Collectively Evaluated	1,225,372	1,227,574	1,270,834
Total ending balance	1,257,750	1,261,145	1,279,167
Legacy Loans [Member] | Home Equity Receivable Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated	5,522	4,763	1,307
Ending Balance: Collectively Evaluated	715,315	719,928	713,592
Total ending balance	720,837	724,691	714,899
Legacy Loans [Member] | Credit Card Receivables Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated	2,060	2,202	2,836
Ending Balance: Collectively Evaluated	138,558	144,154	139,028
Total ending balance	140,618	146,356	141,864
Legacy Loans [Member] | Residential Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated	18,076	17,398	13,031
Ending Balance: Collectively Evaluated	409,206	394,426	384,801
Total ending balance	$ 427,282	$ 411,824	$ 397,832