Loans and Leases (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
PCI loans	$ 1,044,064	$ 1,044,064	$ 1,186,498	$ 996,280	$ 1,029,426
Noncovered loans pledged to secure debt obligations	$ 3,690,000	3,690,000	3,160,000
Threshold period past due for write-off of Business credit card loans (days)	120 days
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	$ 2,590,000	2,590,000	2,200,000
Advances from Federal Home Loan Banks	520,300	520,300	240,300
Federal Home Loan Bank Advances, Current Borrowing Capacity	2,070,000	2,070,000	1,960,000
Loans and Leases Receivable, Gross, Carrying Amount, Covered	296,500	296,500	485,300
Non-PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccruing	87,276	87,276	44,005
Accretion Income	4,500	15,600
PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccruing	5,329	5,329	33,422
PCI loans	1,044,064	1,044,064	1,186,498
Bancorporation
Financing Receivable, Recorded Investment [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Purchase Discount Remaining	45,100	45,100	$ 61,200
Sun American Bank
Financing Receivable, Recorded Investment [Line Items]
PCI loans	29,900	29,900
Williamsburg First National Bank
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount, Covered	$ 7,000	$ 7,000