Loans (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	$ 9,850,884	$ 9,611,482	$ 9,814,088
Loans and Leases Receivable, Gross	$ 16,225,450	15,490,889	16,076,945
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	$ (4,900)	(4,600)	(4,100)
Days past due for nonaccrual status credit card loans	120 days
Acquired Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance	$ 370,600		548,200
Net reclassifications from nonaccretable to accretable	7,753	12,995
Covered impaired loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	306,600		404,400
Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	628,030	1,011,170	677,149
Loans and Leases Receivable, Gross	1,633,706	2,324,879	$ 1,743,071
Covered impaired loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net reclassifications from nonaccretable to accretable	1,673	$ (56)
George Washington and Midwest Acquisition | Non-Single Family Loss Share Agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	122,100
George Washington and Midwest Acquisition | Single Family Loss Share Agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	$ 70,700