Loans (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	$ 9,610,290		$ 9,500,665	$ 9,610,290	$ 9,500,665	$ 9,498,770
Time period for non-payment of loans that are placed on non-accrual status	90 days
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	$ 4,200		6,400	4,200	6,400	5,400
Days past due for nonaccrual status credit card loans	120 days
Acquired Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net reclassifications from nonaccretable to accretable	$ 6,780	$ 27,992	6,646		36,659
Covered impaired loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	335,200		520,300	335,200	520,300
Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	778,414		1,272,244	778,414	1,272,244	$ 1,086,899
Covered impaired loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net reclassifications from nonaccretable to accretable	1,785		8,684	3,865	20,290
Impaired loans | Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance	$ 466,300		$ 659,700	$ 466,300	$ 659,700