Loans and Allowance for Loan Losses (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) loan	Sep. 30, 2018 loan	Sep. 30, 2019 USD ($) loan	Sep. 30, 2018 USD ($) loan	Dec. 31, 2018 USD ($)
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	$ 222,860		$ 222,860		$ 187,295
TDRs both accruing and nonaccruing	162,000		162,000		224,600
Unfunded commitment to borrowers related to modified TDR	2,000		2,000		2,100
TDRs and loans impaired with minimum aggregate relationship balances			1,000
Consumer [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	16,874		16,874		16,744
Real estate in process of foreclosure	8,900		8,900		7,100
Real estate acquired through foreclosure	2,700		2,700		1,800
Troubled Debt Restructurings [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	$ 101,100		$ 101,100		$ 85,500
Number of TDRs subsequently defaulted | loan	0	0	0	0
Troubled Debt Restructurings [Member] | Commercial Non-Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Equity securities			$ 6,800
Troubled Debt Restructurings [Member] | Loans With Extended Amortization Terms Or Other Payment Concessions [Member]
Accounts Notes And Loans Receivable [Line Items]
Extended terms and other payment concessions			600	$ 50,700
Troubled Debt Restructurings [Member] | Loans With Significant Covenant Waivers [Member]
Accounts Notes And Loans Receivable [Line Items]
Covenant waivers			22,100	14,600
Troubled Debt Restructurings [Member] | Loans With Other Modifications [Member]
Accounts Notes And Loans Receivable [Line Items]
Other modifications			$ 7,400	$ 29,100