Fair Value Measurement (Schedule Of Reconciliation Of Assets And Liabilities Measured At Fair Value Using Significant Unobservable Inputs (Level 3) On A Recurring Basis) (Details) - Level 3 - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Junior Subordinated Debentures
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Junior subordinated debentures, beginning balance	$ 277,155	$ 262,209
Junior subordinated debentures, change included in earnings	3,775	4,680
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Change In Fair Values Included in Comprehensive Income	1,683	0
Junior subordinated debentures, purchases and issuances	0	0
Junior subordinated debentures, sales and settlements	(4,203)	(3,284)
Junior subordinated debentures, ending balance	278,410	263,605
Junior subordinated debentures, net change in unrealized gains or (losses) relating to items held at end of period	5,458	4,680
Interest Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	5,874	6,294	$ 4,752	$ 4,076
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings	(1,253)	797
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Change In Fair Values Included in Comprehensive Income	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobserved Inputs, Purchase And Issuance	6,433	10,649
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobserved Inputs Sales And Settlements	(4,058)	(9,228)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Period Increase (Decrease)	5,874	6,294
Mortgage Servicing Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Mortgage servicing rights, beginning balance	153,151	142,973
Mortgage servicing rights, change included in earnings	5,079	(7,670)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Change In Fair Values Included in Comprehensive Income	0	0
Mortgage servicing rights, purchases and issuances	6,530	7,041
Mortgage servicing rights, sales and settlements	0	0
Mortgage servicing rights, ending balance	164,760	142,344
Mortgage servicing rights, net change in unrealized gains or (losses) relating to items held at end of period	$ 8,434	$ (3,955)