Allowance for loan losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Activity within the allowance for noncovered loan losses:
Certain Loans Acquired in Transfer, Accretable Yield	$ (147,576)	$ (196,525)	$ (147,576)	$ (196,525)
Noncovered Loans [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	103,849	114,690	107,699	114,690
Charge-offs	15,015	20,958	32,432	43,770
Recoveries	6,249	5,317	11,687	11,111
Provision for noncovered loan losses	8,766	10,138	16,895	27,156
Allowance for loan losses, ending balance	103,849	109,187	103,849	109,187
Noncovered Loans [Member] | Commercial Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	37,172	31,649	32,363	29,764
Charge-offs	(5,231)	4,274	(11,934)	(8,989)
Recoveries	1,510	188	2,055	714
Provision for noncovered loan losses	6,876	803	17,843	6,877
Allowance for loan losses, ending balance	40,327	28,366	40,327	28,366
Noncovered Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	27,778	33,128	31,857	32,026
Charge-offs	(2,100)	2,608	(2,769)	(4,459)
Recoveries	564	47	645	48
Provision for noncovered loan losses	944	2,379	(2,547)	5,331
Allowance for loan losses, ending balance	27,186	32,946	27,186	32,946
Noncovered Loans [Member] | Commercial Construction Financing Receivable Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	5,124	7,639	5,173	7,180
Charge-offs	0	1,337	(38)	(2,695)
Recoveries	40	293	303	374
Provision for noncovered loan losses	(17)	1,281	(291)	3,017
Allowance for loan losses, ending balance	5,147	7,876	5,147	7,876
Noncovered Loans [Member] | Finance Leases Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	334	480	341	475
Charge-offs	0	127	0	(127)
Recoveries	1	2	38	34
Provision for noncovered loan losses	23	(2)	(21)	(29)
Allowance for loan losses, ending balance	358	353	358	353
Noncovered Loans [Member] | Installment Financing Receivable Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	14,753	20,709	17,981	21,555
Charge-offs	(3,696)	6,202	(8,934)	(14,293)
Recoveries	3,005	3,718	6,185	7,437
Provision for noncovered loan losses	(1,033)	(136)	(2,203)	3,390
Allowance for loan losses, ending balance	13,029	18,089	13,029	18,089
Noncovered Loans [Member] | Home Equity Receivable Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	6,269	6,883	6,766	7,217
Charge-offs	(1,465)	2,762	(3,789)	(5,577)
Recoveries	593	483	1,238	1,182
Provision for noncovered loan losses	52	2,538	1,234	4,320
Allowance for loan losses, ending balance	5,449	7,142	5,449	7,142
Noncovered Loans [Member] | Credit Card Receivables Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	6,520	8,712	7,369	11,107
Charge-offs	(1,645)	2,297	(3,228)	(4,615)
Recoveries	465	557	1,095	1,204
Provision for noncovered loan losses	1,350	1,431	1,454	707
Allowance for loan losses, ending balance	6,690	8,403	6,690	8,403
Noncovered Loans [Member] | Residential Portfolio Segment [Member]
Activity within the allowance for noncovered loan losses:
Allowance for loan losses, beginning balance	5,899	5,490	5,849	5,366
Charge-offs	(878)	1,351	(1,740)	(3,015)
Recoveries	71	29	128	118
Provision for noncovered loan losses	571	1,844	1,426	3,543
Allowance for loan losses, ending balance	$ 5,663	$ 6,012	$ 5,663	$ 6,012