Loans and Leases (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Purchase Discount Remaining	$ 30,100		$ 33,300
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	6,360,000		6,360,000
Advances from Federal Home Loan Banks			175,200
Federal Home Loan Bank Advances, Current Borrowing Capacity	6,170,000		6,180,000
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	100		100
Loans and Leases Receivable, Gross, Carrying Amount, Covered	53,900
Federal Reserve Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	2,230,000		2,190,000
Loans held for sale	53,232		45,505
Proceeds From Sales of Loans	123,047	$ 138,538
Proceeds from sales of portfolio loans	0	0
Non-PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccruing	88,958		84,546
Remaining discount	89,400		95,500
Accretion Income	3,200	2,900
PCI Loans
Financing Receivable, Recorded Investment [Line Items]
Nonaccruing	1,700		1,300
Accretion Income	17,800	$ 18,000
Federal Home Loan Bank of Atlanta
Financing Receivable, Recorded Investment [Line Items]
Advances from Federal Home Loan Banks	175,200
Loans Pledged as Collateral	9,080,000		9,120,000
Federal Home Loan Bank of Chicago
Financing Receivable, Recorded Investment [Line Items]
Advances from Federal Home Loan Banks	14,500
Federal Reserve Bank
Financing Receivable, Recorded Investment [Line Items]
Loans Pledged as Collateral	$ 2,930,000		$ 2,940,000