Summary Of Significant Accounting Policies (Correction Of Immaterial Error Related To Prior Periods) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]
Retained earnings	$ 962,594		$ 962,594		$ 865,427
Interest and fees on loans and leases	121,367	121,322	363,487	365,660
Net interest income	144,890	141,685	432,636	422,759
Loan related fees	4,039	5,308	12,473	15,341
Total non-interest income	48,479	44,691	139,818	134,796
Net income before taxes	64,482	58,158	179,575	153,151
Net income after taxes	44,993	42,231	125,171	108,999
Earnings per common share, Basic (in dollars per share)	$ 0.51	$ 0.48	$ 1.41	$ 1.24
Earnings per common share, Diluted (in dollars per share)	$ 0.48	$ 0.45	$ 1.34	$ 1.17
As Filed [Member]
Summary Of Significant Accounting Policies [Line Items]
Retained earnings		839,816		839,816
Interest and fees on loans and leases		120,018		362,848
Net interest income		140,381		419,947
Loan related fees		6,823		18,071
Total non-interest income		46,206		137,526
Net income before taxes		58,369		153,069
Net income after taxes		42,379		108,886
Earnings per common share, Basic (in dollars per share)		$ 0.48		$ 1.24
Earnings per common share, Diluted (in dollars per share)		$ 0.45		$ 1.17
As Revised [Member]
Summary Of Significant Accounting Policies [Line Items]
Retained earnings		835,741		835,741
Interest and fees on loans and leases		121,322		365,660
Net interest income		141,685		422,759
Loan related fees		5,308		15,341
Total non-interest income		44,691		134,796
Net income before taxes		58,158		153,151
Net income after taxes		$ 42,231		$ 108,999
Earnings per common share, Basic (in dollars per share)		$ 0.48		$ 1.24
Earnings per common share, Diluted (in dollars per share)		$ 0.45		$ 1.17