Loans and Leases (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
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	$ 5,560,000		$ 5,560,000		$ 5,500,000
Advances from Federal Home Loan Banks	835,200		835,200		660,200
Federal Home Loan Bank Advances, Current Borrowing Capacity	4,720,000		4,720,000		4,840,000
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	3,800		3,800		6,700
Loans and Leases Receivable, Gross, Carrying Amount, Covered	73,200		73,200		84,800
Federal Reserve Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	1,990,000		1,990,000
Loans held for sale	154,534		154,534		74,401
Transfer of Portfolio Loans and Leases to Held-for-sale			84,509	$ 0
Carrying Value of Loans Held-for-Investment Sold at a Premium or Discount	32,500		32,500
Gain (Loss) on sale of loans and leases			164	0
Non-PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccruing	88,067		88,067		82,307
Accretion Income	3,000	$ 2,900	6,000	$ 6,100
PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccruing	1,300		1,300		3,500
Accretion Income	20,400
Guaranty Bank
Financing Receivable, Recorded Investment [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Purchase Discount Remaining	17,300		17,300
Cordia Bancorp Inc.
Financing Receivable, Recorded Investment [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Purchase Discount Remaining	3,300		3,300		4,200
Bancorporation
Financing Receivable, Recorded Investment [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Purchase Discount Remaining	22,300		22,300		27,400
Federal Home Loan Bank of Atlanta
Financing Receivable, Recorded Investment [Line Items]
Loans Pledged as Collateral	8,800,000		8,800,000		$ 8,260,000
Federal Reserve Bank
Financing Receivable, Recorded Investment [Line Items]
Loans Pledged as Collateral	$ 2,890,000		$ 2,890,000