Fair Value Measurements (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Investment securities available for sale:
Total investment securities available for sale	$ 5,453,816	$ 6,101,341
Derivatives (other assets)	2,702	1,530
Fair Value, Measurements, Recurring [Member]
Investment securities available for sale:
Total investment securities available for sale	5,453,816	6,101,341
Derivatives (other assets)	88,811	61,301
Liabilities, Fair Value Disclosure [Abstract]
Derivatives (other liabilities)	93,728	66,294
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale:
Total investment securities available for sale	12,882	13,261
Derivatives (other assets)	0	0
Liabilities, Fair Value Disclosure [Abstract]
Derivatives (other liabilities)	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| US Treasury Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	1,104	1,208
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Federal agency securities [Member]
Investment securities available for sale:
Total investment securities available for sale	44	51
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Obligations of state and political subdivisions [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Residential mortgage-related securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Commercial mortgage-related securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Asset-backed securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Other securities (debt and equity) [Member]
Investment securities available for sale:
Total investment securities available for sale	11,734	12,002
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale:
Total investment securities available for sale	5,440,073	6,086,408
Derivatives (other assets)	77,954	55,684
Liabilities, Fair Value Disclosure [Abstract]
Derivatives (other liabilities)	87,959	66,216
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US Treasury Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Federal agency securities [Member]
Investment securities available for sale:
Total investment securities available for sale	25,170	29,716
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Obligations of state and political subdivisions [Member]
Investment securities available for sale:
Total investment securities available for sale	827,385	838,602
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Residential mortgage-related securities [Member]
Investment securities available for sale:
Total investment securities available for sale	4,296,214	4,910,497
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Commercial mortgage-related securities [Member]
Investment securities available for sale:
Total investment securities available for sale	16,947	7,753
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Asset-backed securities [Member]
Investment securities available for sale:
Total investment securities available for sale	213,234	298,841
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Other securities (debt and equity) [Member]
Investment securities available for sale:
Total investment securities available for sale	61,123	999
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale:
Total investment securities available for sale	861	1,672
Derivatives (other assets)	10,857	5,617
Liabilities, Fair Value Disclosure [Abstract]
Derivatives (other liabilities)	5,769	78
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| US Treasury Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Federal agency securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Obligations of state and political subdivisions [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Residential mortgage-related securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Commercial mortgage-related securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Asset-backed securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Other securities (debt and equity) [Member]
Investment securities available for sale:
Total investment securities available for sale	861	1,672
Fair Value, Measurements, Recurring [Member] \| US Treasury Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	1,104	1,208
Fair Value, Measurements, Recurring [Member] \| Federal agency securities [Member]
Investment securities available for sale:
Total investment securities available for sale	25,214	29,767
Fair Value, Measurements, Recurring [Member] \| Obligations of state and political subdivisions [Member]
Investment securities available for sale:
Total investment securities available for sale	827,385	838,602
Fair Value, Measurements, Recurring [Member] \| Residential mortgage-related securities [Member]
Investment securities available for sale:
Total investment securities available for sale	4,296,214	4,910,497
Fair Value, Measurements, Recurring [Member] \| Commercial mortgage-related securities [Member]
Investment securities available for sale:
Total investment securities available for sale	16,947	7,753
Fair Value, Measurements, Recurring [Member] \| Asset-backed securities [Member]
Investment securities available for sale:
Total investment securities available for sale	213,234	298,841
Fair Value, Measurements, Recurring [Member] \| Other securities (debt and equity) [Member]
Investment securities available for sale:
Total investment securities available for sale	$ 73,718	$ 14,673

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.

- Definition

Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

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