Loans and Allowance for Loan Losses (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($) agreement loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 187,295	$ 252,800
TDRs both accruing and nonaccruing	224,600	219,700
Post-Modification outstanding recorded investment	94,760	177,070	$ 132,234
Recorded investment		20,800
Unfunded commitment to borrowers related to modified TDR	2,100	7,300
TDRs and loans impaired with minimum aggregate relationship balances	1,000
Related party balances of loans	37,500	33,600
Related party new loans	16,300
Related party repayments	12,300
Short-term borrowings	1,589,128	1,703,890
FHLB Borrowings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Short-term borrowings	1,160,104	1,132,567
Troubled Debt Restructurings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	85,500	$ 99,200
Number of TDRs subsequently defaulted | loan		0
Troubled Debt Restructurings [Member] | Loans With Extended Amortization Terms Or Other Payment Concessions [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Post-Modification outstanding recorded investment	50,800	$ 98,100	108,900
Troubled Debt Restructurings [Member] | Loans With Significant Covenant Waivers [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Convenant waivers	14,600	76,200	22,800
Troubled Debt Restructurings [Member] | Loans With Other Modifications [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other modifications	29,400	2,800	$ 500
FDIC Loss Share Agreement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loss share agreements | agreement			1
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	16,744	15,087
Post-Modification outstanding recorded investment	$ 455	40
Number of TDRs subsequently defaulted | loan	1
Real estate in process of foreclosure	$ 7,100	7,500
Real estate acquired through foreclosure	1,800	3,400
Consumer [Member] | Troubled Debt Restructurings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment	100
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	35,866	40,480
Post-Modification outstanding recorded investment	1,297	$ 2,812	$ 694
Residential Mortgages [Member] | Troubled Debt Restructurings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDRs subsequently defaulted | loan			1
Recorded investment	$ 200
Commercial Non-Real Estate [Member] | Troubled Debt Restructurings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDRs subsequently defaulted | loan			4
Commercial Real Estate - Owner Occupied [Member] | Troubled Debt Restructurings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of TDRs subsequently defaulted | loan	1
Recorded investment	$ 1,800