Fair Value Measurements Asset and Liabilities Measured at Fair Value on a Recurring Basis (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Investment securities available for sale:
Investment securities available for sale, fair value	$ 4,840,035	$ 4,926,758
Trading Assets	49,402	70,711
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	52,430	76,343
Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	4,428	3,845
Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	4,835,091	4,922,433
Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	516	480
Fair Value, Measurements, Recurring [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	4,840,035	4,926,758
Trading Assets	58,540	82,125
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	62,561	80,110
Fair Value, Measurements, Recurring [Member] \| US Treasury Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	1,003	1,004
Fair Value, Measurements, Recurring [Member] \| Federal agency securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Obligations of state and political subdivisions (municipal securities) [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	702,727	801,188
Fair Value, Measurements, Recurring [Member] \| Government-Sponsored Enterprise (GSE) [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	3,617,080	3,798,155
Fair Value, Measurements, Recurring [Member] \| Private Label [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	3,159	6,149
Fair Value, Measurements, Recurring [Member] \| Commercial Mortgage Backed Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	429,108	228,166
Fair Value, Measurements, Recurring [Member] \| Asset-backed Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	24,924	0
Fair Value, Measurements, Recurring [Member] \| Other Debt And Other Equity Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	62,034	92,096
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	4,428	3,845
Trading Assets	0	0
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| US Treasury Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	1,003	1,004
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Federal agency securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Obligations of state and political subdivisions (municipal securities) [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Government-Sponsored Enterprise (GSE) [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Private Label [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Commercial Mortgage Backed Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Asset-backed Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Other Debt And Other Equity Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	3,425	2,841
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	4,835,091	4,922,433
Trading Assets	54,980	74,331
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	58,008	79,963
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US Treasury Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Federal agency securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Obligations of state and political subdivisions (municipal securities) [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	702,727	801,188
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Government-Sponsored Enterprise (GSE) [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	3,617,080	3,798,155
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Private Label [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	3,159	6,149
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Commercial Mortgage Backed Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	429,108	228,166
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Asset-backed Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	24,924	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Other Debt And Other Equity Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	58,093	88,775
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	516	480
Trading Assets	3,560	7,794
Liabilities, Fair Value Disclosure [Abstract]
Trading liabilities	4,553	147
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| US Treasury Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Federal agency securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Obligations of state and political subdivisions (municipal securities) [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Government-Sponsored Enterprise (GSE) [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Private Label [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Commercial Mortgage Backed Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Asset-backed Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Other Debt And Other Equity Securities [Member]
Investment securities available for sale:
Investment securities available for sale, fair value	$ 516	$ 480

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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