Fair Value Accounting (Financial Instruments Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	$ 4,801	$ 5,097
Investment securities available for sale	3,582,244	3,587,818
Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	193,896	210,004
Collateralized Mortgage Obligations Issued By U.S. Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	550,055	529,597
State And Municipal Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	4,039	4,434
Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	20,058	19,803
U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	43,706	43,357
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,622,134	2,630,419
Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	8,204	$ 9,672
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	15
Investment securities available for sale	55,044	$ 56,102
Private equity investments	0	0
Derivative assets	0	0
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	4,786	5,097
Investment securities available for sale	3,525,562	3,529,971
Private equity investments	750	870
Derivative assets	35,958	27,139
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities available for sale	1,638	1,745
Private equity investments	26,757	27,148
Derivative assets	0	0
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	4,801	5,097
Mortgage loans held for sale	62,867	59,275
Investment securities available for sale	3,582,244	3,587,818
Private equity investments	27,507	28,018
Mutual funds held in Rabbi Trusts	11,035	10,664
Derivative assets	35,958	27,139
Trading account liabilities	1,573
Derivative liabilities	36,409	27,445
Fair Value, Measurements, Recurring [Member] | Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	2,727	2,922
Investment securities available for sale	193,896	210,004
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Obligations Issued By U.S. Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	395	1,078
Investment securities available for sale	550,055	529,597
Fair Value, Measurements, Recurring [Member] | State And Municipal Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	1,481	1,097
Investment securities available for sale	4,039	4,434
Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	198
Investment securities available for sale	20,058	19,803
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	43,706	43,357
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	13,550	13,623
Fair Value, Measurements, Recurring [Member] | Securities Issued By U S Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	126,602	126,909
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,622,134	2,630,419
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	8,204	9,672
Fair Value, Measurements, Recurring [Member] | Interest Rate Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	33,788	25,580
Derivative liabilities	34,232	26,030
Fair Value, Measurements, Recurring [Member] | Mortgage Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2,170	1,559
Derivative liabilities	762
Fair Value, Measurements, Recurring [Member] | Trading Account Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading account liabilities		1,032
Fair Value, Measurements, Recurring [Member] | Visa Derivative [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	1,415	1,415
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	15	0
Mortgage loans held for sale	0	0
Investment securities available for sale	55,044	56,102
Private equity investments	0	0
Mutual funds held in Rabbi Trusts	11,035	10,664
Derivative assets	0	0
Trading account liabilities	0
Derivative liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Collateralized Mortgage Obligations Issued By U.S. Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | State And Municipal Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	15
Investment securities available for sale	3,134	3,073
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	43,706	43,357
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | US Government Agencies Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Securities Issued By U S Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	8,204	9,672
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Interest Rate Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Mortgage Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative liabilities	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Trading Account Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading account liabilities		0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Visa Derivative [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	4,786	5,097
Mortgage loans held for sale	62,867	59,275
Investment securities available for sale	3,525,562	3,529,971
Private equity investments	750	870
Mutual funds held in Rabbi Trusts	0	0
Derivative assets	35,958	27,139
Trading account liabilities	1,573
Derivative liabilities	34,994	26,030
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	2,727	2,922
Investment securities available for sale	193,896	210,004
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Collateralized Mortgage Obligations Issued By U.S. Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	395	1,078
Investment securities available for sale	550,055	529,597
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | State And Municipal Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	1,481	1,097
Investment securities available for sale	4,039	4,434
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	183
Investment securities available for sale	15,286	14,985
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | US Government Agencies Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	13,550	13,623
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Securities Issued By U S Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	126,602	126,909
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	2,622,134	2,630,419
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Interest Rate Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	33,788	25,580
Derivative liabilities	34,232	26,030
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Mortgage Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2,170	1,559
Derivative liabilities	762
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Trading Account Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading account liabilities		1,032
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Visa Derivative [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Mortgage loans held for sale	0	0
Investment securities available for sale	1,638	1,745
Private equity investments	26,757	27,148
Mutual funds held in Rabbi Trusts	0	0
Derivative assets	0	0
Trading account liabilities	0
Derivative liabilities	1,415	1,415
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Collateralized Mortgage Obligations Issued By U.S. Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | State And Municipal Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	0
Investment securities available for sale	1,638	1,745
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | US Government Agencies Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Securities Issued By U S Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Interest Rate Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Mortgage Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative liabilities	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Trading Account Liabilities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading account liabilities		0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Visa Derivative [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	$ 1,415	$ 1,415