Fair Value Measurement (Schedule Of Fair Value Assets And Liabilities Measured On Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	$ 80,797	$ 80,165
Investment securities available for sale	2,890,475	2,814,682
Loans held for sale, at fair value	481,541	513,431
Residential mortgage servicing rights, at fair value	94,346	115,010	$ 158,946	$ 169,025
Derivatives	383,884	150,574
Total assets measured at fair value	3,931,043	3,673,862
Junior subordinated debentures, at fair value	195,521	274,812
Derivatives	34,820	8,808
Total liabilities measured at fair value	230,341	283,620
Foreign currency derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	792	626
Derivatives	600	456
Investments in mutual funds and other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	70,247	67,133
Equity securities held in rabbi trusts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	10,191	12,147
Other investment securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	359	885
U.S. Treasury and agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	750,512	643,604
Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	252,419	261,094
Residential mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	1,887,544	1,909,984
Interest rate lock commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	23,727	7,056
Interest rate forward sales commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	1,161	105
Derivatives	26,092	1,351
Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	358,204	142,787
Derivatives	8,128	7,001
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale, at fair value	0	0
Residential mortgage servicing rights, at fair value	0	0
Total assets measured at fair value	63,102	64,243
Junior subordinated debentures, at fair value	0	0
Total liabilities measured at fair value	0	0
Level 1 | Foreign currency derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	0	0
Derivatives	0	0
Level 1 | Investments in mutual funds and other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	52,911	52,096
Level 1 | Equity securities held in rabbi trusts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	10,191	12,147
Level 1 | Other investment securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	0	0
Level 1 | U.S. Treasury and agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Level 1 | Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Level 1 | Residential mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Level 1 | Interest rate lock commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	0	0
Level 1 | Interest rate forward sales commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	0	0
Derivatives	0	0
Level 1 | Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	0	0
Derivatives	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale, at fair value	481,541	513,431
Residential mortgage servicing rights, at fair value	0	0
Total assets measured at fair value	3,749,868	3,487,553
Junior subordinated debentures, at fair value	0	0
Total liabilities measured at fair value	34,820	8,808
Level 2 | Foreign currency derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	792	626
Derivatives	600	456
Level 2 | Investments in mutual funds and other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	17,336	15,037
Level 2 | Equity securities held in rabbi trusts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	0	0
Level 2 | Other investment securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	359	885
Level 2 | U.S. Treasury and agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	750,512	643,604
Level 2 | Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	252,419	261,094
Level 2 | Residential mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	1,887,544	1,909,984
Level 2 | Interest rate lock commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	0	0
Level 2 | Interest rate forward sales commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	1,161	105
Derivatives	26,092	1,351
Level 2 | Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	358,204	142,787
Derivatives	8,128	7,001
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale, at fair value	0	0
Residential mortgage servicing rights, at fair value	94,436	115,010
Total assets measured at fair value	118,163	122,066
Junior subordinated debentures, at fair value	195,521	274,812
Total liabilities measured at fair value	195,521	274,812
Level 3 | Foreign currency derivatives
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	0	0
Derivatives	0	0
Level 3 | Investments in mutual funds and other securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	0	0
Level 3 | Equity securities held in rabbi trusts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	0	0
Level 3 | Other investment securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity and other investment securities	0	0
Level 3 | U.S. Treasury and agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Level 3 | Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Level 3 | Residential mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale	0	0
Level 3 | Interest rate lock commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	23,727	7,056
Level 3 | Interest rate forward sales commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	0	0
Derivatives	0	0
Level 3 | Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	0	0
Derivatives	$ 0	$ 0