Allowance for loan losses (Details 1) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010
Legacy Loans
Total ending balance	$ 8,099,928
Commercial Portfolio Segment [Member]
Legacy Loans
Total ending balance	2,981,002
Commercial Real Estate Portfolio Segment [Member]
Legacy Loans
Total ending balance	2,124,760
Commercial Construction Financing Receivable Portfolio Segment [Member]
Legacy Loans
Total ending balance	299,209
Finance Leases Portfolio Segment [Member]
Legacy Loans
Total ending balance	84,507
Installment Financing Receivable Portfolio Segment [Member]
Legacy Loans
Total ending balance	1,262,877
Home Equity Receivable Portfolio Segment [Member]
Legacy Loans
Total ending balance	766,840
Credit Card Receivables Portfolio Segment [Member]
Legacy Loans
Total ending balance	142,586
Residential Portfolio Segment [Member]
Legacy Loans
Total ending balance	438,147
Noncovered Loans [Member]
Allowance for loan losses
Individually evaluated for impairment	10,991		7,080	6,416
Collectively evaluated for impairment	92,858		100,619	102,771
Financing Receivable, Allowance for Credit Losses	103,849	103,849	107,699	109,187	114,690	114,690
Legacy Loans
Ending Balance: Individually Evaluated	121,282
Ending Balance: Collectively Evaluated	7,978,646
Total ending balance			7,748,944	7,408,219
Noncovered Loans [Member] | Commercial Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	(5,327)		(2,497)	(290)
Collectively evaluated for impairment	(35,000)		(29,866)	(28,076)
Financing Receivable, Allowance for Credit Losses	40,327	37,172	32,363	28,366	31,649	29,764
Legacy Loans
Ending Balance: Individually Evaluated	25,250
Ending Balance: Collectively Evaluated	2,955,752
Noncovered Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	1,977		1,599	3,169
Collectively evaluated for impairment	25,209		30,258	29,777
Financing Receivable, Allowance for Credit Losses	27,186	27,778	31,857	32,946	33,128	32,026
Legacy Loans
Ending Balance: Individually Evaluated	33,145
Ending Balance: Collectively Evaluated	2,091,615
Noncovered Loans [Member] | Commercial Construction Financing Receivable Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	115		99	1,038
Collectively evaluated for impairment	5,032		5,074	6,838
Financing Receivable, Allowance for Credit Losses	5,147	5,124	5,173	7,876	7,639	7,180
Legacy Loans
Ending Balance: Individually Evaluated	5,204
Ending Balance: Collectively Evaluated	294,005
Noncovered Loans [Member] | Finance Leases Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	0		0	0
Collectively evaluated for impairment	(358)		(341)	(353)
Financing Receivable, Allowance for Credit Losses	358	334	341	353	480	475
Legacy Loans
Ending Balance: Individually Evaluated	0
Ending Balance: Collectively Evaluated	84,507
Noncovered Loans [Member] | Installment Financing Receivable Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	1,773		1,382	662
Collectively evaluated for impairment	11,256		16,599	17,427
Financing Receivable, Allowance for Credit Losses	13,029	14,753	17,981	18,089	20,709	21,555
Legacy Loans
Ending Balance: Individually Evaluated	31,043
Ending Balance: Collectively Evaluated	1,231,834
Noncovered Loans [Member] | Home Equity Receivable Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	(22)		(31)	(20)
Collectively evaluated for impairment	(5,427)		(6,735)	(7,122)
Financing Receivable, Allowance for Credit Losses	5,449	6,269	6,766	7,142	6,883	7,217
Legacy Loans
Ending Balance: Individually Evaluated	6,063
Ending Balance: Collectively Evaluated	760,777
Noncovered Loans [Member] | Credit Card Receivables Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	128		108	28
Collectively evaluated for impairment	6,562		7,261	8,375
Financing Receivable, Allowance for Credit Losses	6,690	6,520	7,369	8,403	8,712	11,107
Legacy Loans
Ending Balance: Individually Evaluated	1,998
Ending Balance: Collectively Evaluated	140,588
Noncovered Loans [Member] | Residential Portfolio Segment [Member]
Allowance for loan losses
Individually evaluated for impairment	1,649		1,364	1,209
Collectively evaluated for impairment	4,014		4,485	4,803
Financing Receivable, Allowance for Credit Losses	5,663	5,899	5,849	6,012	5,490	5,366
Legacy Loans
Ending Balance: Individually Evaluated	18,579
Ending Balance: Collectively Evaluated	419,568
Legacy Loans [Member]
Legacy Loans
Ending Balance: Individually Evaluated			111,610	92,237
Ending Balance: Collectively Evaluated			7,637,334	7,315,982
Total ending balance	8,031,998		7,635,776	7,216,015
Legacy Loans [Member] | Commercial Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated			8,269	3,573
Ending Balance: Collectively Evaluated			2,767,207	2,466,295
Total ending balance			2,775,476	2,469,868
Legacy Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated			36,087	45,008
Ending Balance: Collectively Evaluated			2,018,849	2,040,050
Total ending balance			2,054,936	2,085,058
Legacy Loans [Member] | Commercial Construction Financing Receivable Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated			9,320	9,407
Ending Balance: Collectively Evaluated			268,015	243,972
Total ending balance			277,335	253,379
Legacy Loans [Member] | Finance Leases Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated			0	0
Ending Balance: Collectively Evaluated			73,530	57,634
Total ending balance			73,530	57,634
Legacy Loans [Member] | Installment Financing Receivable Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated			33,571	15,703
Ending Balance: Collectively Evaluated			1,230,094	1,243,369
Total ending balance			1,263,665	1,259,072
Legacy Loans [Member] | Home Equity Receivable Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated			4,763	1,242
Ending Balance: Collectively Evaluated			739,219	737,477
Total ending balance			743,982	738,719
Legacy Loans [Member] | Credit Card Receivables Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated			2,202	2,453
Ending Balance: Collectively Evaluated			144,154	141,375
Total ending balance			146,356	143,828
Legacy Loans [Member] | Residential Portfolio Segment [Member]
Legacy Loans
Ending Balance: Individually Evaluated			17,398	14,851
Ending Balance: Collectively Evaluated			396,266	385,810
Total ending balance			$ 413,664	$ 400,661