Loans (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	$ 9,802,573	$ 9,656,751	$ 9,802,573	$ 9,656,751	$ 9,814,088
Loans and Leases Receivable, Gross	16,343,606	15,705,110	$ 16,343,606	15,705,110	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	(3,300)	(5,400)	$ (3,300)	(5,400)	(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	340,900		$ 340,900		504,700
Net reclassifications from nonaccretable to accretable	4,883	8,217	12,636	21,212
Covered impaired loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	301,200		301,200		351,100
Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Commercial	554,414	877,598	554,414	877,598	677,149
Loans and Leases Receivable, Gross	1,488,636	2,095,684	1,488,636	2,095,684	$ 1,743,071
Covered impaired loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net reclassifications from nonaccretable to accretable	699	$ 2,136	2,372	$ 2,080
George Washington and Midwest Acquisition | Non-Single Family Loss Share Agreement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	115,800		115,800
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	$ 65,000		$ 65,000