Note Allowance for loan losses (Troubled debt restructuring according to their accruing status) (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	$ 122,821		$ 139,011
Commercial
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	53,350		68,456
Construction
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	116		725
Mortgages
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	43,909		44,162
Leasing
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	548		607
Consumer
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	24,898		$ 25,027
Non Covered Loans
Troubled Debt Restructuring
Troubled debt restructurings	1,198,526	$ 1,151,343
Non Covered Loans | TDR
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	114,138	106,184
Non Covered Loans | Commercial
Troubled Debt Restructuring
Troubled debt restructurings	253,986	254,532
Non Covered Loans | Commercial | TDR
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	44,667	37,355
Non Covered Loans | Construction
Troubled Debt Restructuring
Troubled debt restructurings	1,035	2,480
Non Covered Loans | Construction | TDR
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	116	264
Non Covered Loans | Mortgages
Troubled Debt Restructuring
Troubled debt restructurings	825,615	774,496
Non Covered Loans | Mortgages | TDR
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	43,909	44,029
Non Covered Loans | Leasing
Troubled Debt Restructuring
Troubled debt restructurings	2,108	2,400
Non Covered Loans | Leasing | TDR
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	548	573
Non Covered Loans | Consumer
Troubled Debt Restructuring
Troubled debt restructurings	115,782	117,435
Non Covered Loans | Consumer | TDR
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	24,898	23,963
Covered loans
Troubled Debt Restructuring
Troubled debt restructurings	5,553	6,596
Covered loans | TDR
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0	0
Covered loans | Mortgages
Troubled Debt Restructuring
Troubled debt restructurings	5,553	6,596
Covered loans | Mortgages | TDR
Troubled Debt Restructuring
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0	0
Non-Accruing | Non Covered Loans
Troubled Debt Restructuring
Troubled debt restructurings	218,957	234,273
Non-Accruing | Non Covered Loans | Commercial
Troubled Debt Restructuring
Troubled debt restructurings	86,784	88,117
Non-Accruing | Non Covered Loans | Construction
Troubled Debt Restructuring
Troubled debt restructurings	868	2,259
Non-Accruing | Non Covered Loans | Mortgages
Troubled Debt Restructuring
Troubled debt restructurings	117,475	130,483
Non-Accruing | Non Covered Loans | Leasing
Troubled Debt Restructuring
Troubled debt restructurings	576	609
Non-Accruing | Non Covered Loans | Consumer
Troubled Debt Restructuring
Troubled debt restructurings	13,254	12,805
Non-Accruing | Covered loans
Troubled Debt Restructuring
Troubled debt restructurings	2,432	3,268
Non-Accruing | Covered loans | Mortgages
Troubled Debt Restructuring
Troubled debt restructurings	2,432	3,268
Accruing | Non Covered Loans
Troubled Debt Restructuring
Troubled debt restructurings	979,569	917,070
Accruing | Non Covered Loans | Commercial
Troubled Debt Restructuring
Troubled debt restructurings	167,202	166,415
Accruing | Non Covered Loans | Construction
Troubled Debt Restructuring
Troubled debt restructurings	167	221
Accruing | Non Covered Loans | Mortgages
Troubled Debt Restructuring
Troubled debt restructurings	708,140	644,013
Accruing | Non Covered Loans | Leasing
Troubled Debt Restructuring
Troubled debt restructurings	1,532	1,791
Accruing | Non Covered Loans | Consumer
Troubled Debt Restructuring
Troubled debt restructurings	102,528	104,630
Accruing | Covered loans
Troubled Debt Restructuring
Troubled debt restructurings	3,121	3,328
Accruing | Covered loans | Mortgages
Troubled Debt Restructuring
Troubled debt restructurings	$ 3,121	$ 3,328