Loans and Allowance for Loan Losses (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) loan	Mar. 31, 2018 USD ($) loan	Dec. 31, 2018 USD ($)
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	$ 204,831		$ 187,295
TDRs both accruing and nonaccruing	223,400		224,600
Unfunded commitment to borrowers related to modified TDR	8,500		2,100
TDRs and loans impaired with minimum aggregate relationship balances	1,000
Consumer [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	17,880		16,744
Real estate in process of foreclosure	7,300		7,100
Real estate acquired through foreclosure	2,200		1,800
Troubled Debt Restructurings [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	$ 105,900		$ 85,500
Number of TDRs subsequently defaulted | loan	0	0
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	$ 100	$ 48,400
Troubled Debt Restructurings [Member] | Loans With Significant Covenant Waivers [Member]
Accounts Notes And Loans Receivable [Line Items]
Covenant waivers	8,800	14,600
Troubled Debt Restructurings [Member] | Loans With Other Modifications [Member]
Accounts Notes And Loans Receivable [Line Items]
Other modifications	$ 6,400	$ 200